Hello Mike,
Your design scenario is the way most UCS customers using the Nexus 1000V have their environments deployed.
The OP is considering using fabric failover with that single vNIC just for the management and vMotion traffic.
I am not sure why his Cisco CSE believes that approach should be recommended, but it is a valid design. The single vNIC would still have uptime in case of single fabric failure with UCS fabric failover enabled on the vNIC.
Regards,
Trevor
@VMTrooper