In Photos 3.0 (from macOS 10.13 High Sierra) there is apparently two distinct ways to delete photos.
Delete by holding Command in the menu, or Command+Backspace (⌘⌫).
Or delete by holding Option+Command in the menu or Option+Command+Backspace (⌥⌘⌫).
What is the difference?
If there is no difference, why is there two different keyboard shortcuts?