I'd personally appreciate if you found and linked to all the places you got your sources. Not only should you anyway, but I'm personally curious about this and want to look more into it.
What I find really strange about this is that, at least, in my opinion, it'd be really dumb to intentionally code your game so that every trainer you fight will miss 1/4 of the attacks they use, which is a pretty massive amount and a huge handicap. Even if you're trying to make the game easier, I feel like 1/4 is far too much. Second, the number 64/256 keeps popping up. Why isn't is simplified to 1/4? I believe that 256 is a significant number for probabilities in older games, at least, from what I've seen, however, it doesn't really make sense why it's not just simplified to 1/4, as it's much easier to comprehend 1/4.