was there a reason ssb64 was not allowed to use the custom stages in 19XX? why were they even allowed to use 19XX? did nintendo say no last minute?

I wasn't a TO, but it would have made no sense to introduce stages in top 8 that were not available the rest of the tournament. There is absolutely no way we could have offered 19XX-only counterpicks to all 239 entrants on only a handful of everdrives.