Not sure about Fed but this would be correct for NCAA. Rule 6-3-6a.
Here's the explanation for the NFL scenario.
http://refs.ws/20tbwasedit: can't get a link to the specific section so here's the verbiage:
Slow walking a touchback
The Washington Football Team is the first to touch their punt at the 8-yard line. Safety Troy Apke catches the ball and then trots off into the end zone. Conventional wisdom says that this is downed at the 8, but hold on.
Let's say this is a play at the goal line. If the ball is caught at the 1 by the kicking team and the player remains outside of the end zone, it is downed there. But in the same situation, if that player's momentum takes him into the end zone, it's a touchback. Basically, if you are going to make that touchback-saving catch, you have to put a period on the sentence and keep the ball out of the end zone.NBC rules analyst Terry McAulay said common sense should prevail, but this play is specifically called out in the NFL casebook, a supplement to the rulebook with sample plays for interpretation.
There is no wiggle room in here for not ruling a touchback, and frankly there should not. Players on the kicking team should know the rules on downing punts, so why put an exception in there for something like this that doesn't also open the door for other plays that it should exclude?
And if this feels like déjà vu, this did happen in 2017 in a game on NBC. And Washington slow walked the touchback in that game. The referee that day? Terry McAulay.