I shouldn't have used the word "contradiction" there when "point of confusion for me" would have been better. I laid out my confusion in the second paragraph of my last post. If momentum of any type is coupled to the gravitational field then why is only one type of momentum (apparently) capable of creating black holes? Now I'm stuck thinking about what would make angular momentum intrinsically different from linear momentum, and so far, I do not appreciate the difference. Having momentum "vary depending on position" seems terribly arbitrary to me when trying to identify a difference. We could easily have a stream of water whose linear momentum increases as we get further from the shore.