Sure, it is still a guess but a better one than humans can make.
It knows people have teeth, but the teeth are only estimated, not real teeth. Maybe they have been copied from some other face. The point is, it is not her teeth.
Imagine it was low res car photo with unreadable plates. "Enhancing" them this way would not bring back the plates. It could paste some plates, because we know this part of car usually has plates, but the real information (actual registration number) is already lost and can't be brought back this way.
In any photo some detail has been lost. This is trivially proven, as the amount of detail in the actual scene was many, many orders of magnitude more than in the photo file.
Detail that has been lost cannot be recovered, it can only be replaced with something that makes contextual sense which is what AI is doing here.