The lines parallel “you are one of them” with “musk is part of gazelle blood”: both suggest a shared origin. The person's distinction and musk's valued character represent exceptional rank emerging from that shared origin.
The poet does not claim that a human literally becomes musk. The point is that belonging to a class does not logically rule out remarkable superiority within it.
The account of musk reflects a traditional literary conception; analyzing the analogy does not require treating it as a scientifically verified account of musk production.