Have you really looked at the tail. In one of your pics it looks like he/she has curved pointed feathers sticking out indicating roo. Girls have rounded feathers, boys have pointed feathers (not the design on the feathers but the feathers themselves). I have red sexlinks and they can have very large, red combs early. I would guess it is a boy, not based on the comb but based on the tail.
I am sorry to say that even hatcheries mess up sometimes with the sexlinks - I ended up with a boy with my order but he started out with some red and then turned pure white. If I am not mistaken (feel free to correct me if I am wrong) but McMurray buys it's eggs from breeders which means that it is possible that they are not always getting what they think. I just think that if they are buying eggs from breeders it is possible they got eggs from a breeders who's extra roo slipped in with the girls or a roo managed to mate through the wire (yes that happens) or something else.