EX3700 "Virtual" MAC Addresses - Why?

A question about range extenders came up in another forum and part of the question was, "what is it with the 'virtual' MAC addresses that the EX3700 creates (a) for itself and (b) for devices attached to the EX3700?"

The EX3700 User Manual makes no mention of virtual MAC address.

One thing it does if totally mess up device IP assignment on the primary WiFi router.  I have a laptop that is assigned 192.168.1.21 in the LAN Setup table.  When I connect to the WiFi router with an ethernet cable, that is the IP address that it gets.  But, if I connect to the EX3700 with an ethernet cable, it gets dumped into the DHCP pool because the MAC address is different.  I can find no setting to say, "Don't DO this."  Can someone explain the purpose of this behavior or point to a Netgear reference?

Thanks