Use of "crossover" on official crossovers

What's our policy for tagging crossover on official crossovers, such as Super Smash Bros. or Street Fighter 6?

With the announcement of Tifa Lockhart joining Street Fighter 6, I was wondering this and I noticed that the crossover wiki doesn't really say anything on the matter.

Is post #11544673 a crossover when it's explicitly about them officially being in the same game?

Is post #11556677 a crossover when they are in the same game but it's not explicitly about that?

Is post #11552618 a crossover when it's about Tifa being in Street Fighter 6 but the others aren't?

Is post #11420147 a crossover when the fight is taking place on Final Destination, so explicitly in Super Smash Bros.?

Is post #11510993 a crossover when there isn't anything in the post really connecting them to Super Smash Bros. aside from them both being in it?

(Related to topic #17497, which didn't really lead to much it seems.)

I think this should be something we should reach a decision on and add a clause to the crossover wiki.

My opinion by the way is that they should all be tagged crossover, if someone is searching for tifa_lockhart crossover, they will want to see her interacting with characters from other franchises, no matter if they're from a game she was in as a guest character or not. But I wanted to ask for clarity since super_smash_bros. -crossover copytags:>2 has a pretty big number of untagged crossovers it seems.

I think official crossover might make for a good tag for these sorts of "official" event crossovers that periodically crop-up, especially in gachas or guest fighters.

I don't think something like Super Smash Bros. should count for it tho, if only to avoid littering it with crossovers, as that is one franchise of a mega crossover. The tag annoys me as is both on and off booru (moreso the latter admittedly, if only because Danbooru allows me more control), but I do understand its purpose and why that happens. But then again, Smash Bros probably is the elephant in the room regarding discussion of this...

There's no pressing need for an official crossover tag when the copyright(s) involved already tell you that there's an official crossover taking place.

Knowledge_Seeker said in forum #445288:

But then again, Smash Bros probably is the elephant in the room regarding discussion of this...

It and similar franchises, like The King of Fighters and Project X Zone.