Unless I'm missing something, the prompt he gave must have been fairly detailed because both games are basically identical.

But for a more practical issue, the ultimate goal of LLMs is to replace software engineers, or at least enable everybody to become a software engineer, to use a more up-beat phrasing that's no less accurate. And so an LLM's ability to reliably construct something from a poorly defined, contradictory, or otherwise flawed prompt, while accurately inferring intent is probably the first finish line.

More likely is the models were trained on similar data.

It's the same prompt but they also gave them the same asset pack.