Both "Create identicons" and "Automatic identicons" only change about half the icons in my contacts.
I am trying to find a pattern here but I see none yet. Nothing to do with spaces, the presence of an address, the country code, if there are messenger accounts linked, nothing.
All of my contacts are on my Device, not in a google account, and many are linked to messengers too.
I am using Lineage OS 16 on a Pixel 2 walleye. Oh, I have Magisk too, it is rooted. Magisk contains the Xposed framework in it.