That CP is dependent upon the durations used to define it is a well-established fact in the scientific literature. Here is the classic reference (note the last author):
The dependency of CP on the test durations used to calculate it is the result of the fact that it is an imperfect model of reality. In particular, the relationship between work performed (distance covered) and duration isn’t truly linear. (Correspondingly, the relationship between intensity and duration isn’t exactly a right rectangular hyperbola.) Of course, proponents of the CP concept like to ignore this “dirty little secret”, because it undermines their narrative that CP is the “holy grail”, which makes them the keepers of the keys to truth.
ETA: I am not the only one who has realized that the emperor has no clothes.
Unfortunately, at the end of the day science is a human endeavor, with those wielding more political power - e.g., by serving as journal editors - having an undue influence on what people believe. Thus, as I constantly harp on my graduate students: learn to think for yourself.)