I'm very surprised you find this workflow more efficient than just writing the code. I find constructing the mental model of the solution and how it fits into existing system and codebase to be 90% of effort, then actually writing the code is 10%. Admittedly, I don't have to write any boilerplate due to the problem domain and tech choices. Coding agents definitely help with the last 10% and also all the adjacent work - one-off scripts where I don't care about code quality.
I doubt it actually is. All the extra effort it takes to make the AI do something useful on non trivial tasks is going to end up being a wash in terms of productivity, if not a net negative. But it feels more productive because of how fast the AI can iterate.
And you get to pay some big corporation for the privilege.