“We typically making very very detailed plans” - this is writing code in English without tests. Admittedly, since generating code is faster, you get faster feedback. Still, I do not think it as efficient as an incremental, test driven approach. Here you can optimize early on for the feedback loop.
You get faster feedback in code, but you won't know if it actually does what it's supposed to do until it's in production. I don't believe (but have no numbers) LLMs speed up the feedback loop.