A whole game, and not one external asset

Matt Shumer's claim is narrower than "AI made a game," and stronger. Claude Opus 5 one-shotted it, and everything in the demo — pictures and sound — is custom code. No external asset.

That constraint changes what you are looking at. A game that imports a pack can look finished for reasons that have nothing to do with the model. A game that draws and synthesises its own pieces can only look finished if the code is doing the art direction too.

He adds "sound on" because the audio is the part you would assume was a file. It isn't. One-shot plus no imports is the whole standard. Either the demo meets it or the caption is just enthusiastic.