Also, it's not just that HE has to be set for a second, the WHOLE offense has to be set for a second at some point in time. He can go in motion without ever coming set at the beginning like he did, if at the end of his motion he, AND everyone else, stops for a full second.
It was so obviously a penalty, made all the funnier by the fact that Troy Aikmann was so adamant that it was a bad call, because he clearly does not, or at least did not, know the rule. And that's one that you'd think that a quarterback would absolutely know.
