Absolutely. All units said in-sync after setting their personas.
Here is our layout:
ISE-ADM-01 Admin-Primary, Monitoring-Secondary
ISE-ADM-02 Admin-Secondary, Monitoring-Primary
ISE-PDP-01 Policy Only
ISE-PDP-02 Policy Only
I synced one at a time starting with ADM-02. After completing the other two boxes. Active Directory Attribs were pulled down when using them in the Ext Group within my Authz rules.