Quite a few weapons (including the newly added Shining Reliquary ones) are made of materials that normally bypass certain DRs, but do not actually have that flag. It is much more likely that the devs use a random weapon they find as a template, paying literally no attention to what it's made of (100% true, thousands of examples), than it is for them to forget to add DR bypass flags on so many weapons. Gotta learn to ignore what the material says unfortunately. It is what it is. Maybe they'll step it up one day.