Of course checking the LLM's output and testing it and iterating on it is factored in. And yeah that verification and testing and iteration where most of the time goes, and still it ends up being significantly faster than typing everything manually, and the end result quality is often higher I believe.

To avoid fighting with the LLM to get right, it's useful to first come up with the architecture manually, run it by the LLM first (without writing any code - just talking to it, asking it to find flaws in your architecture), and once both you and LLM are happy with the plan, fire it to execute. This step removes a lot of friction (but not all of it - later iterations are still almost always necessary)