I have the same issue. Even when I ask it to do code-reviews and very explicitly tell it not to change files, it will occasionally just start "fixing" things.

I find Copilot leans the other way. It'll myopically focus its work in the exact function I point it at, even when it's clear that adding a new helper would be a logical abstraction to share behaviour with the function right beside it.

Overall, I think it's probably better that it stay focused, and allow me to prompt it with "hey, go ahead and refactor these two functions" rather than the other way around. At the same time, really the ideal would be to have it proactively ask, or even pitch the refactor as a colleague would, like "based on what I see of this function, it would make most sense to XYZ, do you think that makes sense? <sure go ahead> <no just keep it a minimal change>"

Or perhaps even better, simply pursue both changes in parallel and present them as A/B options for the human reviewer to select between.