If I recall for both FC and iSCSI:
If you setup Zoning on the FC switches (for FC only) and/or point the iSCSI hosts at the NetApp for login
then I believe things like "fcp initiator show" and "iscsi initiator show" whill show all FC and/or iSCSI initiators talking to ONTAP.
When you go to the GUI/System Manager and try to create an initiator group, I believe it does in fact pull up any WWPN or IQNs that are talking to ONTAP. Now, with WWPNs, what you DO NOT have is which host belongs to to which WWPN. iSCSI typically has the hostname in the IQN so it is easy. With FC< you really need to know what hosts the WWPNs belong to.