It's generating content based on the previous content it encountered - just like a human. As such, it's only plagiarism if a human passes it as their own work (same as they would with a human ghost writer), but then it's the human plagiarising rather than the AI.
This is such baloney. Another way it resembles crypto.
Humans sense, interpret, organize, and consciously feel and experience internal and external stimuli none of which is applicable to stochastic parrots.