If the PR is small enough to naturally fit into a single commit the rebasing vs squashing multiple commits discussion disappears (just please don't merge it!)... there is a single commit.
Many developers make commits that are “wip” with messages to match. Maybe you commit before you go to lunch, or when you go home for the day. These are useless commits and should be rebased or squashed, but many of these same devs won’t do that unless you force them or the tooling does it for them automatically. A minority of devs build a clean history of commits that tells a story, carefully crafted over time (usually manufactured after the fact with liberal use of rebase). For these devs squash is awful. Unfortunately they are truly a minority and the majority ruins things for them.