I don't think it's common for a lower rank, young player to have a lunch with Federer (unless they have some connections e.g. same agents). IMHO, his Swedish coach probably has something to do with it.
Tsonga once said that when Federer entered the room, everybody was quiet, like the boss was coming
Also in various interviews, players normally hang out with their own pals, mainly from the same country. A young player (sorry I don't remember who) once said that in the player's lounge/restaurant, there were tables for the big guys (Federer, Safin (when he was playing). I think ages/generations also help creating groups (in addition to ranking/performance/country).
Anyway, it's not a big deal for Grigor or any young player to have that opportunity but still good for him.