So, I have done what I have done in my own research using their general theory, that the signs are astrological/astronomical, but employing what I believe is a more solid methodology for doing the matching. The reason I think that that general theory holds water is not only because I have had success in my own research, but also because the Joseph Smith interpretations of Egyptian Alphabetic characters in Joseph Smith's Egyptian Alphabet and Grammar are overwhelmingly associated with astronomical themes.
There is some evidence that the signs of the Proto-Sinaitic alphabet may also match up with signs from a tradition of an ancient Lunar Zodiac/Calendar, because Moran's research on the Lunar Zodiac seems to have been right in a few instances (but only because of sheer luck, not because of a solid, systematic methodology). But as for the Lunar Zodiac in general, my research on that is preliminary. I have had more luck matching things up with the Babylonian and Solar Zodiacs.
Anyhow, most of the modern alphabets (Latin, Greek, Cyrllic, Hebrew, Arabic, etc.) all have a traditional order, descending from what is called the "Northern Semitic Order." Some are specifically abjads, meaning that they only represent consonantal sounds, and if there are any vowels specified at all, they are with other marks that were invented afterward that sort of resemble something more like punctuation, and are not necessarily required. We read:
For all the adaptations and mutations, the alphabet's order of letters has been relatively stable. In the 1920s, archaeologists found a dozen stone tablets used in a school in Ugarit, a city in what is now Syria, that are from the fourteenth century BC and preserve two orders of the Ugaritic alphabet. One, the "Northern Semitic order" is related to the Phoenician and Hebrew alphabets and features bits and pieces of an order familiar to Modern English speakers: a, b…g, h…l, m…q,r.
As the alphabet traveled around the world, those who adopted it did very little to change the basic order. Looking at this animation from the University of Maryland, you can see how things have remained largely the same between the Phoenicians and Latin. Long strings of letters, like abcdef, remain untouched for thousands of years.
So the order has ancient roots, but where does it come from?
I hate to disappoint you, but we're really not sure. The practice of having the letters in an established order makes sense: It’s easier to teach and to learn. Why some ancient people put them in that specific order, though, is unknown. Whoever did it didn’t leave any record that we know of explaining why they lined the letters up like that.
But this isn’t to say we’re at a total loss. Scholars have plenty of hypotheses about the order, relating to everything from astrology, musical scales, numbers, and poetry. (http://mentalfloss.com/article/29011/why-are-letters-abc-order)
There is also the "Southern Semitic Order." Here are these traditional orders of the characters:
ʾa b g ḫ d h w z ḥ ṭ y k š l m ḏ n ẓ s ʿ p ṣ q r ṯ ġ t ʾi ʾu s2
h l ḥ m q w š r t s k n ḫ b ś p ʾ ʿ ẓ g d ġ ṭ z ḏ y ṯ ṣ
The order of the Latin and Greek alphabets are different, of course, but generally descend from the North Semitic order. Other alphabets, such as the Geez alphabet in Ethiopia, use the South Semitic order. The Proto-Sinaitic alphabet may or may not have used the North Semitic order. There is no certainty there. But ancient Abecedaria (alphabetic sign lists) from Ugarit are found in both traditional orders.
Now, the Egyptian Alphabet itself consists of lists of characters that represent uniliteral sounds (one consonant), biliteral (two consonants), triliteral (three consonant) forms and determinatives (signs that have the purpose of helping to show/elucidate the context and meaning of other characters and also act somewhat as punctuation/word dividers and pronunciation helps). However, these particular characters do not generally match up with the list of characters that were chosen for the Proto-Sinaitic alphabet, and do not represent the same sounds. However, from evidence in Joseph Smith's Egyptian Alphabet and Grammar, there are affinities in the names of characters, such as Joseph Smith's Gamel (Egyptian Kham, Semitic Gamel), Joseph Smith's Beth (Semitic Beth), Joseph Smith's Iota (Greek Iota, Egyptian Irt), and Joseph Smith's Ho-Ha-Oop (Semitic Ho/He).
In the Egyptian system, what we think of as traditional alphabetical characters are the one-consonant forms (uniliterals). Evidence exists for sign lists of these uniliteral characters that follow closely to the South Semitic Order. Similar to the Proto-Sinaitic, the evidence in Joseph Smith's Egyptian Alphabet and Grammar shows that these characters also have astrological/astronomical implementation. But the South Semitic Order and the Egyptian names of the signs also seems to be some inspiration from acrophonic lists of birds, of all things, derived from poems or recitations where bird names were paired with the names of tree, plants or place-names that they were associated with, that started with the same sound acrophonically. There is some evidence that ancient sign lists from Egypt had 25 basic uniliteral characters in them. So, the original idea for the abecedaria (calendrical/astrological/phonetic sign lists) seems to have originated in Egypt. (https://oi.uchicago.edu/pdf/birds_in_the_ancient_egyptian_and_coptic_alphabets.pdf).
However, the evidence from Joseph Smith's Egyptian Alphabet and Grammar shows that other sign-list orders existed that were invented or customized for a particular context or situation. Rather than recitation of some poems, these lists were mnemonic and acrophonic and acrostic. In the case of the Psalms in the Bible, it is acrophonic and acrostic. In the case of the Hor Sensen Papyrus, it is also somewhat acrophonic and acrostic. But the inspiration/purpose for the particular ordering of the signs in the sign lists in the columns around Facsimile #1, it is simply the identity and genealogy of the owner of the Papyrus. The same is so in other similar sections of other copies of the Sensen Papyrus. The important thing is that the sign list in the Hor Papyrus contains many of the uniliteral and determinative characters from the Egyptian Alphabet, and they are identified as being "alphabetic" characters in Joseph Smith's Egyptian Alphabet and Grammar, although the usage of these characters the Sensen document is more properly described as pictographic. So, while it is true that the Sensen Ordering of the Egyptian Alphabetical Characters is different than either the North Semitic or South Semitic traditional orderings, it is still a derived sign list of what may properly be called alphabetic characters. The fact that there were additional orderings in Egypt shows that while some are traditional, others are fluid. Therefore, the Sign List or Abecedarium derived from the Sensen Papyrus is in very deed the Egyptian Alphabet, just in a custom order. And the ancients used it in this very way.