I'm a little late to the Joker discussion but obviously they put in Joker just for the purpose of representing Personal Q2. I mean it's already written in the Book of Unbreakable Rules of Smash Bros Speculation™ that characters are only allowed to be in Smash Brothers if they appeared on a Nintendo console before, so there's no other reason they could have added him.
It's the same reason Cloud's gameplay is themed around spamming Up Air to a beat, to represent the rhythm-based gameplay of Theatrythm Final Fantasy for 3DS. That's also why the pony-tail alt for Joker isn't going to be that red-haired girl but rather Rise Kujikawa, who I just discovered existed through a google search and know nothing about her actual abilities.
Okay but for real though, while it doesn't make a huge difference to me whether Persona 5 makes to Switch or not, I do think it's going to happen. Even if AttP being on the list is weird as heck that Best Buy leak still seems more like an Intern-kun slip up then a "prank" to me. I still feel like it'd be more fishy if it wasn't true then if it was.
Wait why am I calling the Best Buy guy Intern-kun if Best Buy is not a Japanese-based company? Oh gosh first my new avatar and now this I'm turning into a weeb send help.