That doesn't follow. What I think you mean is that by defining the constraints so rigorously, you've basically solved the problem yourself. But that's exactly the point. The LLM isn't the problem solver, it's the execution engine that does the wiring-up and the ticking of boxes. The easy part, arguably, sure. But still considerable effort that can be saved, and that effort may be better spent on the problem-solving + constraint-defining stage.

Mandatory disclaimer that this is not a pro-AI post. I also don't agree that this setup works, anyway. It's a classic Bob Martinism, the idea that writing good enough specifications makes the implementation irrelevant; it's the type of idea that is allergic to reality