Sure, the AI plays the game, says everything makes sense, does this mean it's coherent and consistent? No.

I'd urge you to try this yourself and you'll see how much they miss and misunderstand. They're nowhere near to being close to be able to do that sort of playtesting themselves.

Any game that been 100% made by LLMs in a vibe-coding way where the author does no testing themselves, will guaranteed be an absolutely mess and incoherent. This is the state of the art today at least, who knows what tomorrow will bring.