I always kind of hated how non-committal POs were with that. It seems like any experienced dev knows backlog is effectively /dev/null. So, if you actually treat it as such, you can skip refining stories that will not be tackled any time soon and you can purge stories from backlog aggressively (or work with filters to hide them), so that your board shows actually relevant stuff.
But POs will always be like, oh no, we can’t delete this story that we spent all of 5 minutes to write. It might still be relevant. We must remember that we still need to do this (and then not do it anyways)…