Last play that they analyze on the video.
Woods has caught the short pass and is steaming for the end zone. Watkins is coming across from his route and has a great angle to block the DL that has a chance to tackle Woods. But....the DL's back is turned. Block him now and it could be called clipping. Watkins waits just a beat til he can see the front of the DL, then blocks him just a bit.
Watkins could have blindsided him and put him on his ass, and with the way the play developed a lot of dumber players would have done so and taken a chance on getting a flag that brings back the TD. Watkins does the smart thing instead.