It might be that some bugs were left untouched. It might be that non-gameplay elements were the only things touched. I believe that at least in SF2 there were some changes, though.
In any case, my entire point was more to the effect that this is something that probably needs a deeper examination at some point just to get it 100% cleared. If there ARE changes, they need to be documented. If not, then I eat my words and we know for 100% certainty there too.
There's a rare chance with the Capcom stuff here in that they're some of the only clearly dated material in the entire MAME set. There's actually a chance to dig deep enough to work out what really got changed revision to revision and document it.