Lots of GT kids cross groups and have situational friendships: a chess friend, a friend at lunch, a friend to play outside with, etc.
I know I was one of these kids, and it lasted into high school. I was a jock with a boyfriend who was a straight-A student and a drama geek, but who was on student council, had lots of band friends, etc. I didn't really "fit" any one place at the time. I had lots of friends, but few close friends. But my high school reunions are a blast because I know EVERYONE there and have a sincere interest in knowing what everyone is doing now.
Actually, that has lasted even to today. I have a large circle of aquaintances with whom I like to spend time at different events and situations, but I have a very tight circle of real, close intimate friendships.
Some of that is personality for me, as it may well be for your child. I'm a highly social introvert, so I like people, but I am still pretty guarded. That means I know a lot of people and like them, but I would give my friendship bracelet to my DH!

Does your DS think his friendship situation is a problem? Does he feel lonely? If not, I don't think I'd worry too much about it. Keep an eye on it, maybe. But just casually.