I can't say it's a good rule but I can't say it's a bad rule either. I think the rationale is that when your toe hits going forward out of bounds it's the only part of your foot that touches. When your toe touches with your back to the sideline, the process of your foot landing is a continuous motion of your foot rocking from toe to heel, and if your heel ends up out of bounds your foot is out of bofunds. So I can definitely see the reasoning behind the rule. But then, if any other part of your body hits in-bounds you're in, regardless of whether the whole body part lands in-bounds. So I dunno. Good or bad, though, the rule's been this way forever and works the same for everybody, so whatever.