The flag indicates that he re- established inbounds and touched the ball first. Had he not re established, he would have been out if bounds and no flag. Another ref came in and said it was a force ot, thus negating the penalty. It's clear that's what happened, but the refs did a poor job of explaining that before the review. What I'm not sure of, is who is responsible to call it a force out. Seems the judge right there should be able to see it, but then again he's watching the feet, so maybe that's why another judge came in and was compelled to call it a force out.