USB-C Ethernet adapter - Predefined computer

I have a Dell XPS 15 9560, and we bought a Dell 96NP5 USB-C to Ethernet dongle to go along with it--it shows up as a "Realtek USB GbE Family Controller".

I find the USB dongle's MAC address, and add it into DS 8.1 as a Predefined Computer. I then put a boot flash drive in the laptop, F12, select the flash drive as I've done hundreds of times with other computers no problem, and...

Another computer object is created in DS, with the computer name matching the Dell service tag.

I check the new computer object, and the MAC address lines up perfectly with my predefined computer.

For what it's worth, I have no problems at all with USB-A to Ethernet dongles.

Thoughts?

Thanks!