I don't know why officials have gotten into the habit of getting in front of players after a touchback has been ruled in the end zone. There's no reason for this. We aren't in pads and if a player gets hit, you already have all the tools you need to take care of it (flag, pen/paper for DQ and report, etc.). You don't need to put yourself in jeopardy and the thought that it will prevent someone from making a hit may or may not be true. I expect my whistle to do that and if it doesn't, the player is better protected than I am.
That is what is the NFL guys are expected to do - to mitigate interaction between opponents, since the ball is dead. Players will smack somebody, then claim they didn't hear the whistle, or some other baloney. If we get out into the field of play and make 'big' time out and touchback signals, the onrushing players see us, and either slow up or alter their paths, and generally don't have interaction with opponents.
The NFL guys pass such techniques down to NCAA guys, via clinics or via the Coordinators for a number of conferences (current or former NFL officials).
Personally, I do not move directly in front of a receiver, for reasons you state. But, I do hustle into the field of play - usually getting beyond the yard line of the deep receiver(s), first using a very "big" time out signal (again, as handed down by NFL guys), with repeated blasts with my whistle, then the touchback signal. They see us. They relax. It is good practice.