I agree with some osters; I imagine that this is more a case of aim for the throat and you'll hit the chin kind of thing. Gloves are very bulky, and you'll be very hard pushed to hit the throat. But, the chin being tucked into the throat area means that you are more than likely to hit there. Also, if an opponent has their chin up and you aim for the chin, if they tuck up before it comes in you might miss. But, if you aim fir the throat and they tuck in, you're more likely to hit. I can see the logic behind it - kind of like a moving target being easier to hit logic.