Species designation is vague and fraught with guesses, errors, etc. Species are defined not only by reproductive fidelity and success (which we don’t always know), but also geographically and through time.
This is one example of many instances of the impreciseness of science.
Understood. But it is a pretty firm rule that if two animals can produce offspring that can in turn reproduce then they are the same species. It would seem to me that the Neanderthals were simply a race of humans and not an actual species.
It’s almost as if there is a scientific orthodoxy that tries to define the Neanderthals as a species rather than a race because it seems to fit a certain narrative.