That's indeed strange. However, vSwitches don't do anything else but switching, i.e. no NAT etc.
>>> ... in vsphere I do see that the physical nics show xxx.xxx.xxx.174 for all of the nics ...
Where do you see this. I guess this is an "observed" IP address, which means that the ESXi hosts detected traffic with this address on the network adapter.
>>> ... 9 leases listed all with the same MAC address ...
Is this MAC address assigned to a VMkernel port group or a VM?
André