I don't believe the MAC is retrieved as part of a reconfiguration. I think there may be an idea for that...not sure. Either way, try using CLI update action code 0x10112 on the device model handle before destroying it to see if it populates the new mac (this action code tells Spectrum to retrieve the MAC from the device).
cd to $SPECROOT/vnmsh
./connect
./show models | grep <modelname>
./update action=0x10112 mh=<modelhandle of device>
./disconnect
Cheers
Jay