"The idea being that if you rub the chicken leg on the kitchen surfaces it'll get too dirty to eat?"

I don't know if that's what they're implying, but raw chicken is one of the very worst things you can put on a surface you're going to put other food onto, I can tell you that. The point isn't that the chicken will get dirty if the counter isn't clean, it's that the counter will be rife with really dangerous germs once it's been rubbed with raw chicken meat.

Bob