[rectang]

I don't feel strongly about the issue.

A good clean fast-forward merge of a single-commit PR is fine. But I've also worked at multiple jobs where every merge to the production branch created a merge commit and that's also fine. It adds a bit of complexity to the history graph, but it's not meaningless complexity.

If your commit history is majority single-commit PRs then having additional merge-commits everywhere would be noisy, so in that case it would be too much. I don't tend to work on actively developed projects that match that pattern, though. Most feature development involves multiple-commit branches.