Missed a few calls when a flow I'm running thought everyone was an unknown caller! :-)
That permission is already granted.
Saw this just above the part of the article you linked to; maybe the trouble is related to them moving the permission to a new group?
Restricted access to call logs
Android 9 introduces the CALL_LOG permission group and moves the READ_CALL_LOG, WRITE_CALL_LOG, and PROCESS_OUTGOING_CALLS permissions into this group. In previous versions of Android, these permissions were located in the PHONE permission group.
Thank you again for your heroic support of Automate across all these devices and OS versions!