Yes there is some truth to the physical aspect of the "wall"... but more over I think it is the mental drain that zaps these kids around December.. In college, December for players was studying for tests and screwing off more than getting ready for the next week of ball..
In the pros, there is no month lag for them to get away from the game mentally.. and the mental grind overtakes them... there is no more room for partying with the frat brothers, no more breeze courses to divert your mind from the playbook or the gameplan.. Week after week there is always the next game..
IMO.. that is the brute force of the wall.. the mental grind.
So you ask if coming in late helps that... IMO, no, because right now for instance Raji is playing catchup mood and probably investing more in totality to get caught up to speed on the mental side.. where as some of the others that have made the roster get a bit of a break between the third and fourth week of preseason..
So in the end.. it probably is a wash.. no benefit in alluding the "wall".
Some have it in them to bust right through.. some it smacks them in the face.
"The oranges are dry; the apples are mealy; and the papayas... I don't know what's going on with the papayas!"