The clock starts as soon as someone touches it. You can't fair catch a ball that touches the ground. You can give yourself up and they will call the play dead, but someone would have to fall on the ball cleanly and even then there would certainly be a couple seconds ran off. If the player has a brain fart and runs at all or hesitates then that's even more time. With only 13 seconds left only a moron kicks it out of the endzone. Would you rather even 1 second gone by with the ball in Mahomes' hands or some shitty special teamer?