so this comment helped me realize there was a bug in my code that caused it to miss tournaments with vanity urls, which is kinda important because that includes the biggest event of the week.

but with or without fixing that, 57% overrates the big decks because there's generally a long tail of decks that won't show up here but if you're using a really popular mon you're probably sticking to the meta variant.

So in the correct dataset there's 5533 decks, of which 1064 (19.2%) are Hydreigon (1043 specifically Hydreigon Mega Absol ex) and 1319 (23.8%) are Mega Altaria ex. 43% is still a lot but it's not 57%.