Yeah on second thoughts I won’t experiment with head swaying. My instincts tell me that I’ll just end up with a very sore neck.
He probably sways his head to balance himself. He does seem like an asynchronous runner. I noticed (I think) when he entered the straight he kicks his left knee higher and for the next few steps seems to have a slightly higher left knee then right. In any case he must have very good glute strength to drive from a knee that high at that speed. I can’t get any drive from that position.