Sakurai didn't trick anyone or make anything fake. The "leak" was a hoax from the start. So it's the reverse; the hoax tricked people.
But Sakurai said not to expect too many new fighters, and then said that the rate of characters would go down after the Isabelle reveal. He was very clear in setting our expectations. But people would have rather believed "Ah, he's just trolling" instead and set themselves up for disappointment.
Yeah, this was my biggest issue with this hype cycle. People kept insisting that we shouldn't take Sakurai at face value and extrapolating minor moments of trolling to mean he was trolling us with the roster.
And then I'd get accused of being the hype police and coming off as arrogant and condescending. Perhaps I did, but when Sakurai has made note of a limited number of newcomers
on three separate occasions and all you have is "But Sakurai likes to troll people and would NEVER end of such a disappointing note", then you start to sound illogical and a little bit desperate. Sakurai should be taken as the word of God on the game he's working on. He can change his mind game to game and make characters previously thought to be unviable viable in future entries. He does speak the absolute truth on his own game in the time, or at least trolls so minimally that he's revealed the truth in less than a couple of minutes.
Sakurai told us exactly how he approached the game, people expecting a huge number of newcomers after Isabelle were absolutely setting themselves up for disappointment, Grinch leak or not.