The way I see it, because you can spin up additional AI employees at will (and spin them back down), when the problem with the spec is found, it's no big deal to redo all of that work from before, adjusting for that change.
Ironically, people keep saying this, but then gloss over the core problem of coordinated between these agents... For completely independent codebases with no dependencies, sure thing right on...go for it. But the vast majority of F500 companies I work with have wild and undocumented dependencies between almost every system that will take years to "agentify" (assuming they ever figure out that it's an organization and governance problem.... which they might not ever realize)