What if's are almost universally using characters from alternate universes. Regardless of what universe it happens in, they are alternate versions of a character.
In this situation, it could well be that they ARE the 616 character i.e. they are the same character. Yes, it happened in another universe, but it involves the same characters.
It IS possible the laws of physics in that universe are different, though we have nothing indicating that.
IMO, for the characters actually transported to the HR universe, showings between them are no different than showings in the 616 universe. The location doesn't matter and it is the equivalent of them fighting on the Shi'ar homeworld or whatever.
Or, are you saying that if 616 Thor and Hulk join Exiles, then travel to earth 167, get angry at each other and fight, then the result of that fight is non canon, just because it happened in another location, especially if there is no indication of 'differing laws of physics' or whatever? Even if there were different laws of physics, that the fight would happen between the two 616 versions of the character makes it canon....but, like when Hulk was hampered with Savage Banner, there may be mitigating circumstances.
Now, if it was the Thor construct that it happened to, its more in question, and more likely a non showing.
What I'm saying is events which transpired there occurred in an entirely different time-line. That time-line does not align with 616 continuity.
BRAUGI: Yes, these things didn't happen in the 616 universe. If you look at the 616 universe timeline, they didn't happen.
Yet, if you look at 616 Thor's timeline, they DID happen. He left the 616 universe, and everything that happened to him, happened to that very same version of Thor. Thus, for 616 Thor, whatever happened to him is 'canon' and part of his timeline.