Hi damien,
I have three iOS devices that I am backing up to iCloud, and they all are showing the correct info. My iPad 1 doesn't show it under Device Info, of course, since it is running an ancient iOS, and it doesn't show up on the device list, but even on that device, when I look at the iCloud backup info, it is displaying correctly for the iOS that it is running.
Have you tried signing out of iCloud and then back in again on one of your devices that is not displaying correctly? (If you are using iCloud Photo Library, the photos will be deleted and will have to download to your device again, so that's kind of a pain). But when iCloud is acting weird, signing out of and then back into iCloud will usually rectify the issue if neither a restart nor a reset worked.
Best of luck,
GB