Yeah, I get your intent, but I think there's some conflation of backup and sync.
Here's a hypothetical - imagine you deleted a photo from your phone, and then modified (in place) a different photo.
Is your expectation that the first would be deleted from the various places you have it backed-up? (If not, then what's your process for fully destroying a photo?)
Would the second be propagated to each of your SaaS storage providers overwriting the existing, or renamed and situated adjacent to the original? And if you modified it in-place a second time?
If your phone were then to stop working and needed replacing, would the restoration process restore your phone to before, or after, the above deletions / changes were made? ie. would the deleted photo exist on your phone, would the second photo be pre, mid, or post modifications?
(I draw the distinction between backups and archives whereby backups get you to where you were most recently (pre incident), and archives let you restore to something like 'Tuesday afternoon, two weeks ago'. I'm talking here purely about backups vs sync though.)