I’ve heard the same about McEnroe from a friend who used to to work for him; very kind, generous and genuine guy off the court.
My uncle said the same during the years. He may TALK smack, but they’re just for “drama”. I think every time they went to lunch he picked up the tab. Sampras on the other hand, may be quiet but he got the vibe he’s scheming something which gave him the creeps.