But that's not equivalent. It's like a "all horses are mammals, but not all mammals are horses" kind of logic argument. All telekinetics should be able to fly. They only have to lift themselves as if they were any other object. In fact, since they are themselves, it should be pretty easy to get an idea of how to move the object.

Flight--pure flight--on its own is something else. So, all telekinetics should be able to fly, but not all fliers are telekinetic. And I don't just base that on Marvel. It's true of the telekinetic in The 4400, too. Besides, Nathan might not be levitating. Levitating is what telekinetics can do. He can also speed up or slow down, implying that he has (oh God help me) thrust to his lift off. If he can sonic boom, he ain't just levitatin'.