troy,
did you ever ask him why he did it?
something just feels like maybe he was doing it to strengthen his fluency of phrases/fragments doing it backwards with his fretting hand, or something to this degree. can anyone get in touch with him to ask him why he was experimenting doing this on the guitar?
Hey Brad!
Batio is very active on social media and does a lot of livestreams (e.g. on Facebook) where he takes questions from the viewers. Probably your best bet is to tune in on one of them 
i dont really use facebook. 
i have been kinda tinkering with more fingerstyle, and i know they use ring middle and index combination from what i believe would be because when you close your fist thats the natural way your fingers curl. so when you tap them on a table this is the most natural sequence, and will probably be the fastest. so in this thinking i was thinking about the fretting hand last night and remembered he flipped over the top. so using this same logic if you reverse it on your fretting hand the ascended chromatic is now more natural to finger. which means all of the fragments that are ascended are now more natural. just thought maybe he might have been doing this for that reason, or to somehow workout his brain when he was training to play left handed. using this as sort of a brain relaxation for ascending fragments making it easier on his right hand when it started to fret. and to me it just feels like that it was more than just a showmanship thing to show off on stage. like he was doing it for other reasons.
MAB, aside from being a phenomenal player, is a great showman. Iād bet the ranch that the reasons he does the overhand fretting at times is not technical at all and he just thinks it looks cool and flashy. Maybe an edge case would be if there are very wide stretches, because I think thatās easier since it allows the wrist to be in a more advantageous position, like a piano player. And I think I have seen him do the overhand thing with wide stretches.
But to your point about the ordering of fingers used, my classical teacher always told me that it was āeasierā to go from weaker fingers towards the stronger. He said thatās why classical tremolo (ignoring the thumb) is a-m-i and not i-m-a. So from this it would follow that if the pinky was included, itās easier to do c-a-m-i as opposed to i-m-a-c. Certainly, if I just sit at a table and tap my fingers I have an easier time going faster when I start with the pinky.
@Tom_Gilroy has done extensive research on left hand speed and concluded that combinations involving ring/pinky are always slower that index/middle/ring or index/middle/pinky. As far as I understood, in terms of speed potential there was no difference in a forward or reverse pattern as long each finger always was allowed to rest the period of the 2 other fingers being used.
Iāve never heard him comment on the scenario of, if one must do ring/pinky in succession, if there is a natural preference for ascending or descending.
i dont mean its really a technical thing just a way to play certain things more naturally by the flow of falling fingers. it would be hard to use your right hand to fret if you naturally pick with it so i was wondering if maybe he did it first with his right to teach it how to fret then took it to his left for the showmanship thing.
i might have to disagree because you have to ask yourself could you 3 finger picado pick with the opposite sequence as fast as the more naturally relaxed ring middle index. i just dont believe that would be possible.
I have to agree with @joebegly that he does it simply for showmanship. Iāve gone to a couple of his clinics and chatted with him a little, and while I never explicitly asked this question, as I recall he said he did these things because nobody else had done them, and was trying to be as outrageous as possible. Itās also worth noting heās nowhere near as skilled with his trick techniques (left hand over the top,.over/under, playing lefty, etc) as he is when playing with a normal setup.
Yeah I know what you mean. Itās what I was trying to say about a classical tremolo. (Almost) everyone does it a-m-i. I canāt get as much speed going i-m-a. But is that just convention, or is it because of mechanics? I donāt know. Iāve definitely put tons more time into the traditional way. At the same time, that seems like saying descending scales could be played inherently faster than ascending due to the order of (fretting hand) fingers used. I donāt know that itās generally accepted that this the way things are
bingo thats what i was thinking last night 
sadly i would be to old to see if this could help speed up my ascending fragment fingerings lol
This may be too tangential, but I remember a violin teacher teaching what she called āthe thumbless tortureā to break the habit of squeezing the neck. Basically, you play without any thumb support.
Always thought it was just a cool trick. Rudy Sarzo does this on bass some times.
No idea why MAB does it but it seems one of his students does it as well usually with harmonics.
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When I saw Tom playing with the E Street Band he did this trick in a couple of his solo spots as well.