If the Church were strict about this practice, it would insist that priests only wash the feet of other men in Holy Orders, since the Apostles were the first bishops.
Well, natch! They appoint them and all - wink, wink, nudge, nudge! Kinda like a dog chasing his own tail. I don't mean to be disrespectful at all (not equating dogs with bishops) but it seems to me that the bishops and their own liturgy commission would be kind of redundant?).