Again, I think people are antsy for news and are therefore trying to find ways to confirm their favorites ahead of time.
A character getting a Mii Costume doesn’t suddenly make them more likely. If that’s the case, then Dunban, Chrom, Flying Man, Proto Man, Viridi, and Lloyd Irving should also be considered frontrunners.
A critical flaw of the Smash fan base is that they splice evidence in ways they, as in individual fans, see fit. The evidence is fitted to support their favorite, even if it would support another character as well.
This is where I see the “Rex and Pyra would never be a Greninja situation because it’s not the same thing”, or “Ashley is more likely because she hasn’t been seen just yet and had a Mii Costume”. It seems to me that the only reason Rex and Pyra can’t be a Greninja situation is because particular people don’t like Rex and Pyra because “muh sexualization”, and people are just ignoring the fact that there are still 20 something remaining Assist Trophies we haven’t seen and assuming it “increases a characters chances” when that’s not necessarily the case.
With the AT’s, there’s just as much of a chance they got cut. We were literally shown footage from a demo. The purpose of a demo is to show some, but not all, of a given product. For all we know, Sakurai felt we needed something fresh and replaced Shadow with Knuckles. Or we have both Shadow and Knuckles as AT’s.
Support the characters you want and talk about how cool they will be. I’m not saying we shouldn’t do that. But one thing I see happening over and over again is this expectation that “X CHARACTER IS GOING TO PLAYABLE” and then when X character is, indeed, not playable, fans get mad about it when the expectation was entirely fabricated by the fans themselves.