I watched that video, and I find that the points he makes are relatively good and I agree them simply on the basis of logically selling these characters.
Imagine following up Joker and the content in this pack with...a first party character that doesn’t have nearly as much interesting content to pull from.
It wasn’t Erdrick that caused speculation to change, and I don’t believe that was the point. Sakurai specifically tweeted about how each DLC pack will bring in spirits. It won’t just be Joker. It will be all 5 picks.
If you don’t think Spirits deconfirm fighters, then that’s fine, I don’t blame you. However, I would also suggest really considering the implications of that. Based on the several Mario spirits in the game, what would go on the DLC board for that character? Pokémon? Zelda? The spirits would be redundant at this point.
However, the only logical loopholes I can think of would be either Gen 8 Pokémon or Three Houses, because you can absolutely add a new stage, new characters as spirits, and new music. Despite this, I still personally find 1st parties to be at a clear disadvantage.
I also think there are new logical conclusions we can come to. Spirits, Mii Fighter costumes, and substantial content beyond that could quite possibly disconfirm arguably hundreds of characters. Spirits may not have been meant to disconfirm fighters, but that doesn’t matter much if all DLC is 3rd party.
With this in mind, the main cast of Sonic is spoken for. A large portion of the Street Fighter cast is spoken for. If the Wii U Mii Fighter costumes get brought over, and will be revealed as tie ins to soon-to-be-revealed DLC fighters, that means the Monster Hunter Mii Fighter costumes, which mimic the player character (otherwise known as the Hunter people would argue for Smash as playable) , along with the Mega Man costumes, would be revealed alongside a playable character from a Capcom franchise.
If the Twitter poll conducted by Hideki Kamiya is considered a soft disconfirmation, Dante and Amaterasu are out of the running, which would mean Resident Evil has no competition as the next Capcom Franchise. (This is a weaker point, mainly because who knows if Kamiya actually knows anything. We also already know Dante is out of the running as it is.)
Namco could potentially be in the same boat, and it may come down to Tekken or Tales. Both series had a Mii Fighter costume, and would need to reveal the previous ones in order to bring back old and new Mii Fighter outfits.
With this in mind, Square Enix will probably get Erdrick, and will reveal the Chocobo, potentially Dragon Quest costumes, and of course Geno. This brings back content from Wii U, introduced by the induction of a new character.
I think those implications are entirely possible. You folks expecting a first party should be careful, just saying. Don’t get yourself hyped up for disappointment.