Maybe we shouldn't be paying too much attention to the accuracy of what the laddie is wearing, but rather with his purpose in wearing it in the first place. The woman with her back to us is wearing a costume; perhaps he thinks he is, too (perhaps he even borrowed it, incomplete, for the occasion). In fact, the only one in the photo who is not wearing a costume is the woman in the centre. It's the "costume" part we are objecting to, isn't it?