Do you mind trying to explain what exactly should happen in such a play?   A defensive player just suppose to reach down and tap him sort of congratulating him on getting every inch possible in his "safety slide"  Love me some Cam dude plays to the extreme
(fwiw) I'm not insinuating such play is acceptable every time all the time  It's actually not so fair that a guy like TB12 who may not be able to get near the same yardage in such a play isn't actually punished near as often  More the nature of the beast that it can happen  Defensive players hope to intimidate and prevent  Watching the play it doesn't really look like the DB can really pull back  It may not matter so much but just re-watching the play it appears Cam is sizing up the defenders' pre-play for his ability to make yards on a rush  
https://youtu.be/Rw8XScipo2k
 I'd totally respect an answer which suggests that other QB's are held just as accountable for such plays