Actually there are some kids or people that are 2700-3000 on chess.com but only 2200 on tournaments just because they don't compete enough so it depends it would be unlikely but it could actually happen
I think dramatically underrated players coming up suddenly out of the woodwork is going to become steadily more common moving into the future and more players will be attaining their titles via tournaments. Perfectly valid.
Actually there are some kids or people that are 2700-3000 on chess.com but only 2200 on tournaments just because they don't compete enough so it depends it would be unlikely but it could actually happen