I would agree with your points if not for the fact that "clean up commits" or "typo fix" is a necessary result of PR's.

Your teammate will request changes in your code, and the only way to cleanly communicate "yes I made that change, and ONLY that change" is through these clean-up commits.

Otherwise, if you amend/force-push or open an entirely new PR, 99% of the diff are things that your team has already seen and reviewed.

Squash merges let you clearly communicate how you addressed PR comments, while also keeping the master history clean.