The ruleset in Japan might be slightly different than in the USA and europe but no so much that the difference in regards to Pit would be notable. The BBR ruleset has no ledge grab limit and actively supports planking as a tactic - the japanese ruleset has often a ledge grab limit, uses air time in case of a timeout and has no counterpicks where Pit could make notable use of his flexibility.
All in all the US ruleset is a better basis for Pit to be successful than the japanese.
Saying the japanese have a different metagame is a strawman. Point in case is that the japanese have simply developed the character far more than the US did. Earth placed top 20 at Apex and he's not even the best Pit in Japan. Masashi has taken sets off a player who placed 7th or 8th at Apex [his Falco and his MK] and most of the japanese top players as well.
You can't say that Brood's success doesn't matter because japan has a different metagame. So what? He's still good enough to beat two of the world's best players at the same tournament and he's not even the best Olimar in japan.
Are results from Europe and America the only things that matter? It's sad to see that people disregard the japanese when they are obviously better at this game.