You're basically describing a waterfall process. That never worked in a pre-AI world and won't work in an AI world. Why? Because it's just not possible to gather absolutely every requirement up front. Software development has always worked well as an iterative process. You come up with better solutions as you go along and learn about the problems you're solving and make improvements. While AI will be able to one-shot a set of requirements, you'll miss out on those improvements because you'll have skipped over those phases.

I've tried this out. Even with relatively small applications and with spending hours reviewing the spec documents, there was always something I missed or something that wasn't quite right when seeing it live.