Spirits disconfirm, easily. While other made-up fan rules are often stupid enough for people to disregard on their premise alone, Spirits disconfirming did have some merit to it, at least when it came to the base game: If a character had a Spirit shown in prerelease, then they most definitely weren't getting in because playable characters didn't have normal Spirits like that, and if they were going to reveal a character, they wouldn't have them shown as some random Spirit before they decided to reveal them.
Post-release, however, was a different story. Since the DLC was most likely chosen after all of the Spirits were decided, the total Spirit count covers over 1000 potential characters, and since it would be utterly asinine for them to limit their options because of a bunch of .png files, the possibility was open for Spirits to be upgraded. Despite this, people would swear up and down that it would be impossible for them to add a DLC character who was also a Spirit.
Whether it be for lore reasons (Spirits are the very essence of a character and if they're in the game already, they can't be made into a fighter.), past precedent (We've yet to get a Spirit upgrade, so it's most likely not happening), percieved popularity (I mean, those characters were made into Spirits for a reason, right?), or even simply because they believed the devs cared about silly things like that, this point would be endlessly parroted for many months after release, even as contrary evidence continued to pile up.
Seeing this fan rule get obliterated with the reveal of Min Min was so incredibly satisfying that it motivated me to make this video in celebration. If that isn't representative of how much I relished it's destruction, then I don't know what else to say except that Spirits don't disconfirm.