not sure if i should have put down resolved but we have it working as follows:
1) we only still see one initiator in Nimble pointing the initiator name from fabric A.
2) in the iSciBootvSwitch, we added another port group & added the vNic & IP info for initiator from fabric B
3) we are still seeing only the one initiator from fabric A, but we are "guessing" that could just be a pointer label, as we tested this theory by removing access for that initiator in Nimble & it did not drop the connection. we still have further tests to carry out.
i logged a case with VMware about this & they sent me the following kb link
as initially we created a new vswitch to add the vNic for the initiator from fabric B & when we try to bind it to the iSCSI adapter, it showed as not in use. linked to point 2 above.
4) we installed the Nimble PSP package on each ESXi host.
dont know if this helps, but i can try & help if you have any further questions.