no where does this document suggest that codex can "one shot everything to perfection with just a prompt". It describes using a prompt plus agent skills (which are essentially many other prompts) to develop a playable game.. nothing about it being perfect or anything more than being in a playable state.
Besides, other people's claims about something doesn't give you license to abandon all critical thinking. Though it's evident they don't claim what you say they are.
To be clear that's not what I'm thinking, even Fable 5 produces some hilariously bad results under some conditions and sonnet 5 produced great results under others.
But you didn't provide the evidence for that. You shared some links and then admitted they didn't claim it.
It kinda seems like "because I think they're a little too positive about their product, I can set my expectations to anything I want and la-la-la it's their fault."
And I don't see the problem with agents building test scaffolding as they go. It might be too defensive at times, like testing a shell script you don't run often, but big deal. It's kinda cool imo, and it's trivial to make it stop.