Yeah, not saying it isn't, or shouldn't be, a foul during a free kick down. But it is specifically referenced under scrimmage kicks, but not referenced at all under free kicks. The definitions support a foul, but the penalty isn't prescribed there (nor should it be). In my humble opinion, this is an oversight by the Rules Committee and/or Sec-Ed. And, as I look back to my very first rule book (1972), it has been for a very long time.
Just something interesting I discovered while answering a question for one of our brothers.