If you then delete from the Recently Deleted album it says that the photo “will deleted the selected photos from iCloud and all connected devices”.
Additionally, at least in iOS 17.5, the Recently Deleted album itself has a disclaimer at the bottom that says that “items will be permanently deleted. This may take up to 40 days.”
iCloud is a pile of crap with eventual consistency everywhere, including some really extreme interpretations of "eventual": I've had deleted "favorite places" on Maps persist for years. Deleting them would hide them from the local device, yet restoring a brand new device would bring them back.
The whole thing feels like it's running on duct tape, wishful thinking and a large chunk of non-technical users that would blame themselves rather than the shitty tech when weird things like this happen.
> When you delete photos and videos, they go to your Recently Deleted album for 30 days. After 30 days, they'll be permanently deleted.
https://support.apple.com/en-us/104967