This guy was keeping his options open: he waited to see if A gave up on their coverage, and then he would have run it out. An R killing it just before he took off would have had hell to pay.
Huh? First, he turns his back to the defense. Second, he holds the ball like you would hold a briefcase with his arm loosely hanging down. Third, he wasn't looking at the kicking team coming down the field, he was walking toward the official slowly and casually. NOTHING in his actions showed he was trying to keep his options open.
Should he have taken a knee? Well, that would have settled the issue. He could have walked out of the back of the end zone and this still would a have been a non-issue. But you can't argue that he made ANY motion to "keep his options open" or do anything other than give himself up.
It doesn't appear that in the judgment of the R there was perceptible time during which
the Team B player made no attempt to advance after receiving the free kick.
If that's true, then it was extremely poor judgment. The tape shows there was over six seconds between the receiver gaining possession and when he was hit by the defense. I would much rather think that the R felt the runner needed to take a knee by rule than to think that his judgment was so bad to think that six seconds was not a perceptible time.