it handles the stat that determines how many turns of digestion are decreased at the start of a unit's turn (with dusk lamia being an example of a unit that utilizes being able to change it)
I've continued messing with it, and I still can't get it to work. Using the Aon file as a base, I changed the "DigestSpeed" value from 1 to 2, and nothing else; in-game, there was no difference in how long it took her to digest units. Her displayed Digest Speed value in the barracks did update though.
There may be certain stats that do not have a specific use at the moment, and are more placeholders for when more characters that utilize the faster speed are made. It may also have a specific change needed somewhere else in the code (like an ability addition), but I would have to get back to you if I figured something out.