This could very well be a pattern that some teams evolve into. Specs are the new source -- they describe the architectural approach, as well as the business rules and user experience details. End to end tests are described here too. This all is what goes through PRs and review process, and the code becomes a build artifact.
It just doesn’t work though. Anthropic couldn’t even get Claude to build a working C compiler which has a way better specification than any team can write and multiple reference implementations.