I'm confused. A rocket going out on a long elliptical round trip is the same thing as a linear twin paradox scenario so at what point does the ellipse become circular enough to qualify as HKX reciprocal time dilation with no permanent age difference between the twins? This is contradictory to me saying the HKX is the same as the centrifuge time dilation example (except that the participants are separated at the start in the centrifuge). Since I'll never find anyone who understands the question, let alone the answer, I guess I'll never have these contradictions of circular motion resolved. I'll stick with linear for now and come back to this way in the future.