I can only agree with you unofficially. My understanding has been you should not use any version before SP 0.0 for production work.
PR stands for Pre-Release, not Production Release, so yes it should be considered as a final Beta release, but you should be able to simply open and save it in a production release to update it ... unless SW advises otherwise ... which I believe has happened in the past.
And yes it is probably advisable to uninstall Beta and PR releases before upgrading to a production release.
I noticed the "older version" message as well when I opened a file that I had worked on using PR-1.
I'm with everyone else here - when SP0.1 became available, I backed up, removed PR-1, and did a fresh install with SP0.1
I can't find the image I once had but ..........
Up to SOLIDWORKS 2014(?) when you saved files with PR1 it would show the file: Last Save As - THE ONE AFTER BETA