Of course. The point is that a full, detailed spec isn't enough (even in the rare situations it does exist, like for a C compiler). At least for the moment, you need expert humans to supervise and direct the agents.
Vibe coders usually also let the agents write the tests, which mean that the only independent human validation of the software is some cursory manual inspection. That also obviously isn't enough to validate software.
> One shot doesn't work even with humans - after all, this is exactly what killed waterfall as a methodology.
You can one-shot a C compiler with humans. LLMs' software development ability is impressive and helpful, but it is not human-level yet, even if at some tasks the agents are better than most human programmers. And while many waterfall projects failed, many succeeded (although perhaps not as efficiently as they could have). So far I don't believe agents have been able to produce any non-trivial production software autonomously.