It appears (guess) that FOS or iPXE is seeing two different network adapters as nic0. It is possible to boot FOS Linux from a usb stick. The issue is that the deploy image function you use is a product of iPXE and not avaialble via the FOS Linux usb boot method. With that said there is a hack of the FOS Linux usb boot hack that can simulate the “iPXE Deploy Image” menu.
I posted instructions on how to do this with graphical representation late last year but I can’t seem to find it at the moment. In this post it kind of explains how to do it with the FOS Linux grub menu. https://forums.fogproject.org/topic/12842/fos-boot-usb-quick-image-issue/12
Edit: Ah I found it, look at the last post in this thread: https://forums.fogproject.org/topic/13977/suggestion-please/66?lang=en-US&page=1