When we write the vowels first, I see vestiges. But then we usually go in "font order", that is, K D G H K L M N P (R) S T... you know, the trusty Latin-based alphabetical order.
In the Doctrina Cristiana, however, the Baybayin character order was recorded as A U E H P K S L T N B M G D/R Y NG W. That ain't based on OUR alphabet, bub. And... see the vowels? They're first, like we often still see the characters written.
So there's a datum. Where can I go with that? If I knew more about the Brahmic-related scripts, then I'd compare directly with them.
Next best thing: I'll use the Japanese kana ordering. From Wikipedia:
The gojūon is an ancient convention (somewhere around 1004 to 1028 AD), originating in the character ordering in Sanskrit, as well as a means for expressing the hansetsu of Chinese characters.
Aha. So let's compare the ordering of gojūon with the Doctrina Cristiana order:
* Some differences apply: In Japanese, the kana has its own 'kudlits' which can, for example, turn /HA/ into /PA/ or /BA/ -- /KA/ into /GA/. And Japanese has no /L/ sound -- /R/ is midway between our L and R, and use it in both places. And it has no /NG/.
* h/b/p (はばぱ) are placed where p/b are in Sanskrit (again from Wikipedia). So it looks like Baybayin is closer to Sanskrit order than Kana order, which is perfectly reasonable.
Looks pretty reasonable to assume that Baybayin originally used an old Brahmic ordering. Not surprising. But it's nice to have some evidence for that.