Have this been measured, not comparatively, but absolutely? Where you plan, but don't code, instead leave the task to an agent (while you do something else), then test the result (maybe a quick look at the code), and ship. Is it sustainable? Or is it for greenfield setup and common ideas (things you would use tooling and snippets before)?

> What's left is "planning" which under a modern iterative model apparently includes deployment/distribution and getting/understanding/incorporating feedback.

That is not "planning" means. Planning is usually understanding, research, and design.