(I am having trouble phrasing this question to be unambiguously sincere and without intention of provocation, so please bear with me...)
I read your statement above as saying that "Black" means "descended from US chattel slavery".
Is that your intention? Is this a big-B vs small-b distinction? What are [Bb]lack users called if they are not descended from slavery, or not from US slavery?
Please assume ignorance and not malice. I really do not know what I don't know here.