#2 isn't talking about the wheel being true... the OP is asking if it is true that you should not be able to see the front hub when you're on the hoods, if your stem is the right length.

I think that particular rule of thumb is total BS. If I bend my elbows a little more and change my torso angle only slightly I can go from not seeing the hub at all, to seeing the whole thing with ease. OMGMYFITISWRONG.