Is it possible to do iPhone photo backups on iCloud, without syncing to iCloud Photos?

So I've recently enabled iPhone backups to iCloud. I noticed that the Backup menu says "Photos not backed up- Photos Data is not included in this backup. You can turn on backup for Photos in the Manage Storage section of iCloud settings.". I go to the iCloud photos menu, and there's a toggle asking me to turn on iCloud Photos Sync. Below it, it says "When syncing is off, your Photo Library is included in your device backup. You can change this in iCloud Backup Settings"...

The thing is... I just want to back my device up to the cloud. I don't want my photos to be synced and accessible to my iPad — I want to keep them separate. This makes it seem as though my photos are not being backed up anywhere UNLESS I sync them to the cloud (and then have the view them on my iPad as well). How do I ensure my device backup has a copy of my photos?