Can you elaborate on what about the scale of "a few devices and one user's iCloud backup" makes hard delete challenging? A 30-day period seems like plenty of time to propagate the "Alice really does want to delete this photo on 6/21" message to all devices and all servers where you might have backups.

And even if it is challenging, it shouldn't even need to be said that soft deleting photos of all things would be completely and totally irresponsible. This isn't some metadata in a business app, some of those deleted photos are extremely sensitive.