scenario, that was the laziest, slowest sub I have seen in awhile, it was obvious Utah was slowing the sub hoping to get the ref to stand over the ball, but they were so slow with the sub that the ref walked away.
In that scenario most refs are not going to "give the defense an opportunity to substitute" if the defense is doing so intentionally late to try to take advantage of the play clock, which is why you almost never see subs slow walking like that DL was, they usually are running.
Refs generally don't take kindly to being used for cheap penalties, and that is probably going to not work in Utah's favor if that tactic is used repeatedly, especially when the subs are loafing on and off the field.