There has been quite a debate in the biological sciences on just this matter of words. Is there really that much information conveyed by the word "bird" or "fish," for example. It's true that some people call a whale a fish. As you know, it is very unlike most fish.
But, with respect to the larger sense of your comment: is this another way of saying that the exception proves the rule? Now, I understand this idea in terms of the archaic meaning of the word PROVE, as a kind of testing. And, by this definition, the exception disproves the rule. Possibly people understood this when the phrase was coined.
This is always a very hot issue in music, by the way, since "theorists" are always telling musicians what they can and cannot do, what is and is not music, etc. This has been going on for hundreds of years, and for the most part composers have been happily ignoring it all - with excellent results.
In fact, the "distinctions" you are referring to are words, and just words: hetero, homo, whatever. It is easy to make a rule out of words. Paraphrasing the poet, however, "theory is gray, but life is evergreen."