I've had a handful of software projects in my career land essentially on the day I predicted, sometimes several months out, and the commonality across all of those projects was that the specification was crystal clear. Two of them were actual ports of an existing piece of software over to a new system. And so any time we had a question about the implementation, we could look at the existing version and immediately have our questions answered about what "correct" was.
I think projects where correct is very clearly defined can benefit from LLM acceleration, as you're describing here.
But so much of modern software development is figuring out what the right thing to build is. And in those situations, I don't think LLMs provide nearly as much benefit.