Didn’t he say it was to be revealed.
Out of all the characters that he predicted, he only stated that Ridley would be revealed on E3, as far as im concerned.
Here are the 3 sources from Vergeben that said Ridley was playable:
Source 1 = Bandai Namco developing Super Smash Bros. and Metroid Prime 4 (TBC) + Ridley playable in Smash.
Source 2 = Ridley + Simon Belmont + Ice Climbers (return) in Smash, Just Cause 4 (confirmed), and new Jump game that would be a mix of popular japanese shows (confirmed, Jump Force), 2 Castlevania games (TBC), one compilation game (TBC).
Source 3 = Ridley at E3, with a presence not just limited to being shown playable.
Only the 3rd source states that Ridley was revealed at E3 specifically, the others dind't specify.
Even then, you have Sal Romano's leak that stated that Little Mac, Miis, Wii Fit Trainer, Villager, Mega Man, Pac Man all at E3 2013, but only half of them were revealed (and Lil' Mac wasn't even announced at a E3) so it wouldn't be the first time that a leaker has the content right, but the dates wrong (it's actually quite common among leaks).
Oh and also regarding this whole "dataminers did it first" thing.
Vergeben's Statement of Base Goku and Vegeta playable: November 13, 2017 (this is the earliest archive Internet Wayback Machine offers regarding his post).
Dragon Ball FighterZ release date: Jaunary 26, 2018 Worldwide and Feb 1 in Japan.
So unless some dataminer got a very, very early copy (as in before November 13 2017,) that included data of Base Goku and Base Vegeta in game, Vergeben actually did it first.