I tried to use this on my iPhone XR. It seems to be a nice gimmick and not much more. However, I am running into one issue with one option:
when I try to create a screen with Photo Shuffle, I get a message saying "Photo Shuffle is Processing; When your photo library is processed you can choose from smart photo collections etc. etc." and nothing else happens. That message stays on screen.
Now, I understand that my photo library is a bit large, but then after a few seconds, the screen shuts off (power saving, right?). Then later when I turn my phone on, it displays the lock screen; and then I have to repeat the process of creating a new lock screen with photo shuffle, and then the message shows up again; rinse and repeat.
The only thing I can do it to select photos manually and pick a small subset of my photos (because it takes too much time to individually select pics from around 10000 pics).