You’re assuming that maintainers have a desire to use agentic coding in the first place.

Secondly, it would seem that such contributions would contribute little value, if the maintainers have to write up the detailed plans by themselves, basically have to do all the work to implement the change by themselves.

Open-source maintainers have no investors to placate, no competition to outrun, why would they want to use agentic coding in the first place?