The author of the commit doesn't matter per se. If someone is just having AI summarize their changes and using that as the commit message, I agree that they're doing it wrong.

These days, lots of my commit messages are drafted by AI after having chatted at length about the requirements. If the commit message is wrong or incomplete, I'll revise it by hand or maybe guide the AI in the right direction. That tends to be a much more useful and comprehensive description of the commit's intent than what I would naturally find worthwhile to write on my own.

OP's approach is interesting as well, at least in principle, and if it works well it might be the next best option in the absence of a chat log. It should just make sure to focus on extracting the "why" more than describing the "what".