This is not proof for a leak.
Leak is real: Alright guys hear me out. Someone posted a snapchat video under the name of a guy who worked/works for a company with light ties to Bandai Namco. There is no proof that this company (one of the two companies actually, one has already flat out denied involvement with Smash Bros) actually has anything to do with Smash Bros. This 50 year old guy has decided to risk his entire career by leaking information to one of his friends via snapchat. His friend just happens to be someone interested in Smash Bros too (probably someone close to his age) and decides to risk his friend's career by leaking his snapchat video.
After this gets leaked, Nintendo makes an unprecedented move and tells anyone associated with them that they must either ignore the leak, or make videos about it being fake. Even though these sources have previously talked about leaked characters (some whom they thought were real), for some reason Nintendo put its foot down and didn't allow any conversation about this leak (even though game explain actually made TWO videos about this, I keep seeing people lying saying they didn't make any videos about it). Companies like gamexplain know how much trouble with Nintendo they'll get if they step out of line, so they lie to all of their fans, even though this will all be revealed in less than 2 months. They've decided to jeopardize their relationship with their fans. "Insiders" who've been correctly and incorrectly predicting newcomers now all of a sudden aren't allowed to confirm these characters. The fact that they've "leaked" other characters in the game doesn't seem to matter, and now they've decided to become shills for Nintendo. They've all formed a team dedicated to lying and tricking the Smash fans into believing that this leak is fake.
So... none of my argument above actually prove anything.
I see where you're coming from, and I don't deny that there are a lot of coincidences, and that this is complicated (and some of these are reasons why I can't say with 100% certainty the leak is fake), but complication does not disprove something. I've seen very complicated situations for non Smash leaks in the past, and people used very similar arguments.