Thats wrong. Your comparison with a manual transmission in a car is only valid when having a manual pitch control, but not for constant speed. A csp is a car with automatic transmission where 100% rpm is for "sporty" driving and everything below 100% rpm is for economical driving.
Top Speed is at maximum rpm and maximum boost, just look at historic performance tests, for top speed they always were at maximum rpm and maximum boost. Why would they do this when there was more speed at lower rpm