Annan completely understood.
What taboo had Nicolas Flamel really violated—
It wasn't just a matter of ethics or moral caution; nor was it merely to uphold the authority belonging to gods or monarchs... Although Nicolas had simultaneously challenged his peers, the monarch, and the gods, what truly led to his death was his betrayal of "humanity."
Because if synthetic humanoids were determined to hide, it would be almost impossible to find them with their capabilities.