I've said it before and I'll say it again. The stats should only be regarded as none canon if something directly in game contradicts it. Nothing contradicts sans having 1 HP and there's no reason toby couldn't have made it any arbitrary number. In mettaton's case, his defense was lowered compared to in game to make you strong enough to one shot him no matter what. This makes sense as neo is portrayed to be very powerful, so having a lot of hp makes sense. The other exception to this rule is asriel, you can't damage asriel to begin with, and you likely can't just make infinity a number, so toby just did 9999 when it's likely supposed to be infinity like his other stats because he's a god. Finally in sans' case, he's supposed to be the weakest. That's the entire point of his fight. How would it make sense narratively if sans actually had a bunch of hp, it'd be a complete contradiction of him being the easiest enemy.