I've been hearing "it's not just... it's a" touted as an AI sign recently, personally I think it's an AI sign because it's a human thinking shortcut sign, and AI copies it, but it would be funny if AI wrote the article and then hallucinated this specific money quote.
I doubt this happened here, but FWIW, AI does have a habit of "cleaning up" (read: hallucinating) interview transcript quotes if you ask it to go through a transcript and pull quotes. You have to prompt AI very specifically to get it to not "clean up" the quotes when you ask it to do that task.