>Will anyone be surprised how often it's the former that management will go for?

I don't think I have ever asked permission to do make what I thought was the correct change.

That's because you're not opening Jira tickets titled Refactor Foobar. You're just doing it as a consequence of resolving real business issues. I have seen developers, and once been the developer, suggesting a refactor to the PM. That rarely works: it does not (directly) address a business goal.