My response at full speed is that we have a catch and TD.
At slo-mo, I found myself thinking that was a REALLY good call by the covering official. Clock on the ready.
Frame-by-frame, I see the foot drag and just clip the sideline, which would have put the ball back a yard or two and held the clock for the snap. But honestly, I don't expect him to see that - his focus is rightly on the ball and the goal line. I'm sure as hell not going to criticize for missing the foot, except that he's closer to the sideline than I would prefer here - backing away from the field a couple of yards might have helped him to catch that. If the H has anything to add, he should do so. But I still say that's a damn fine call by the S.