M.S.
Your child is seeking out people he can relate to, who share his interests and mindset. That's what we all do if you think about it. We become friends with, and relate to some people more than others because of our interests, etc.
He will actually be more *socialized* by being able to relate and talk comfortably with adults.
He is his unique self, he is who he is. And if he *enjoys* his playdates with his peers then that's good. He has the best of both worlds. One doesn't need a ton of friends to be happy. To have one or two true friends in this world is a blessing. Is he happy? If he is, not to worry :)
Support his passions, encourage his curiosity and interests and view him as the wonderful, unique person that he is.
He seems to be a freethinker... what the world needs more of.