Guys I crack the code.
Wave 1 will have Isaac, Geno, Chorus Kid and Banjo--Kazooie.
That's why Nintendo tried to shut down the Grinch leak, because it predicted accuratly a bunch of characters.
Sakurai said himself that the roster was finish really early on. + he kept a spot for a pokemon rep. So Isaac AT was made in 2016.
That's why the costume is looking better then the AT, they start working on Isaac before the Rathalos tweet and import is new model on the costume. Thus would explain why we got the trademark for RH and GS. RH and GS are the 2 most represented series in Smash whitout a character.
They had to give the characters designer some work to do when base game characters were done.
Why did we got Weyard and Felix theme but not Isaac theme in Ultimate? Because Isaac theme is getting remix exclusively for Isaac reveal.
Next why did Papa Geno source claim to have heard about a bunch of characters on the Grinch leak? Because a bunch of them were in wave 1.
Why was Isaac AT reveal so late? Because Sakurai thought that the fan would guess Isaac for DLC, or be really made if he was missing, so he hesitate a lot to show him.
If we get ether of these 4 reveal early on, it will look really good for the other characters.
Edit: Now we know that AT can be togle off on some stages, so if someone is playing Isaac, is AT will be off.