it doesn't really align with the option name

+1. It is a bit misleading, even with the documentation change.
Would it be hard to implement sync_changelog=true to not affect the other ways .spec is being processed, like Version, Release updates?
Although I'm not sure if it make sense - if a project is making .spec file changes outside of packit, it might as well handle the rest. Perhaps renaming it from sync_changelog to something that implies it's "syncing the whole spec" would be a way?

Why do projects, like tmt, don't use packit for generating changelog?