For what it's worth (and I realize that's not much), but I agree with youngump.
This yet another place where they clarify something and introduce ambiguity where it is not necessary (as if it is ever). Yes, we all know that the ball that hits both the white and colored portions of 1B is fair. Yes, we know we have a (different) rule to stipulate this. However, there is no reason why we have to insert the word "(only)" here in such a way that we have coaches ejecting themselves over it.
Or was that the intent?