Alright, so for my experience with Mega Man 7, what happened was that because the obsolete TAS was done on the Japanese version and I made my TAS on the USA version, most of the time save was basically eaten... Going from 73 seconds all the way to 31 seconds... Some people who saw the TAS even showed an impression of "Only 31 seconds saved? That is low for the skips used!". It definitely looks like so, because it shouldn't be this small comparing to what people expected. I mostly went with USA version because that is what is preferred and I don't want to disregard that.
For the regional rules, I do agree with allowing Japanese version, just like USA, under a single category of NTSC. Reason for that, as feos stated, people coming to TASing might use Japanese version because that is what they're used to (if they are RTA runners for instance, and prefer it), and still provide optimized TAS. For PAL, that is different story because not just frame rate differences (PAL 50 vs NTSC 60), but also this results in potentially different gameplay, like SMB or Super Metroid (don't have direct examples of this but I heard some cases of these 2 games).
All in all, in my opinion, movie rules should clarify that players are free to use any NTSC official release as long as the gameplay optimizations are increasing (relying on text only is not allowed). Heck, even skipping cutscenes within same region is not a valid reason if gameplay is not optimal. I definitely have some examples of such cases
here,
here and
here (for the last one, please forgive my young self... he was so excited to submit a faster TAS :P)
EDIT:
Rules now do state what I talked about above... And they're in effect already.