It does matter how and where a PR comes from, because reviewers are fallible and finite, so trust enters the equation inevitably. You must ask "Do I trust where this came from?" And to answer that, you need to know where it come from.
If trust didn't matter, there wouldn't have been a need for the Linux Kernel team to ban the University of Minnesota for attempting to intentionally smuggle bugs through the PR process as part of an unauthorized social experiment. As it stands, if you / your PRs can't be trusted, they should not even be admitted to the review process.