How do you define distance and time in relation to a catch though?
I'm not saying you define it by distance or time. Just that a playing going to the ground could be a guy who caught the ball off balance and stumbled for 10 or 15 yards before going down, which is just an absurd possibility.
In application, the rule is trumping the requirements for a completed pass and it shouldn't.
You need possession, 2 feet down, and the time necessary to complete a football move. No move needed, just afforded the time to make a move or ward off contact.
As it stands, a player could begin going to the ground and even though the entire process was drawn out to such an extent that he could have made 3 or 4 football moves, he still wouldn't get credit for the catch.
All they have to do is let the requirements for a completed pass supersede any "going to the ground" and the rule only becomes applicable when a player does not get 2 feet down, or is not afforded the time to make a football move before hitting the ground.
If it were me, I'd restrict it to plays where the player is already in the process of going to the ground. Diving, sliding, or falling while the ball is caught.
That rule has no room on plays like the Dez play. He had possession, got two feet down, and absolutely had time to ward off contact. Had a defender been coming over to hit him, he wouldn't have been lunging.