I think you do need to revise each listing. I haven't found a way to do it in bulk at this stage. Interestingly, if I just hit relist on an unsold item, then submit, the box doesn't automatically tick, but if I hit relist, then make more edits (in the My EBay selling page), the box is ticked. So frustrating because even if I don't want to make edits, I still have to go through all the motion to relist and get the box ticked.