I don't know if true or not, but I do believe that if true that the reaction to it has to do with the perception of why it would be in effect.
The general discussion is that if he doesn't want to be talked to, then it must be because he's just a jerk and not a people person. In other words, Nick is a bad guy.
Another side that isn't put forth so much is that he considers the football complex his workplace and is constantly in a "work" frame of mind, and would not like his thought process to be interrupted with general pleasantries. It's pretty obvious how focused he is, and I don't personally find this hard to believe.
IMO, I recall his comments when he said that his wife pointed out that there was a huge gap between how he thought others saw him versus how they really did (the perception gap). I think this is an example.