It's my opinion, but... him saying he "[took] prestigious works that had survived the test of time" isn't so believable, when he starts off with something from /r/ImaginaryWarhammer and immediately follows it up with a piece from "an unknown Italian Renaissance painter".

Part of it is he's handicapped by having to avoid famous pieces -- but you can still easily find work that outshines these examples. For digital fantasy, art for card games like Magic: the Gathering. For anime, the art for gachapon games is wonderful. For landscapes, he chose a relatively weak Hudson River School painting, and many have more striking composition and lighting that seem very hard to mistake for AI (e.g. https://collectionapi.metmuseum.org/api/collection/v1/iiif/1...).