I think the obvious answer is it's easier to hide in a big organisation than a little one. If an Indy owner is more likely to have eyes on his business then there's no place for a slacker to hide, whether that slacker has loads/no experience. I don't think anyone is carpet stating literally everyone at a stealer is rubbs, there's a few good comments on here about dealers, just on balance Indy's seem to have the right spirit and can't be complacent that the middle class mafia will keep coming back time after time after time just simply because it's a main dealer - regardless of price and customer service.
The other element in my mind is that your average Nissan dealer (non performance place) probably sees one 350/370/GTR for every 500 micras, so they just don't enough trigger time on the big muscle.