Yes, something like that is planned, though I need to do a bit of restructuring in order to make it happen. It's not exactly easy due to dynamic auto-populating playlists which make it difficult to quickly recognize when they've been changed.
This is already possible just by going to all games and choosing selecting them all, then running the wizard. In the future I would like to make this more of an automated process, but for now it should work fine just to run the wizard with all games selected.
Yeah, I think perhaps Download Metadata and Media is not always updating platform metadata like it should. I'll look into that. But yes, it's easy to update community star ratings for one platform just by selecting all games for that platform and running the wizard.