But almost no-one really works like that, and those three separate steps are often done ad-hoc, by the same person, right when the fingers hit the keys.
The promise of coding AI is that it can maybe automate that last step so more intelligent humans can actually have time to focus on the more important first parts.
So we went full circle, again.
Just having requirements and a specification isn't necessarily waterfall. Almost all agile processes at least have requirements, the more formal ones also do have specifications. You just do it more than once in a project, like once per sprint, story or whatever.
Now that agile practitioners have learned that requirements and upfront design actually is helpful, the only difference seems to be that the loops are tighter. That might not have been possible earlier without proper version control, without automated tests, and the software being delivered on solid media. A tight feedback loop is harder when someone has to travel to your customer and sit down at their machines to do any updates.
My feeling is that software developers will need end up working this type of technical consultant role once LLM dominance has been universally accepted.