@doejohn:
An install from scratch - old config happily survived
Factory-reset - Old interface assignments (and maybe other settings? I don't know) still survived
Called the menu to re-assign the interfaces - How can I be sure everything else is at factory reset? Since the interface settings survived the factory reset, maybe some other settings survived too?
The NICs in the default config are assigned as em0 and em1, so on that hardware, a reset to factory defaults would leave you having to re-assign interfaces. The installation process wipes out the entire storage medium, so there's no way that config survived on there. You have an SD card in it that has the config on it that's getting loaded maybe? Your USB flash drive would be completely clean upon rewriting the nano image to it.
I have no idea where the config managed to survive.
I did not use a CF card at all
I used the dd program on linux to write the image onto the raw USB thumb drive. That should have wiped everything what was stored before on that drive, IMHO
My UNIX knowledge comes mostly from linux, so I have no clue about the partitioning scheme on BSD. AFAIK, the partitions are somehow further divided into slices or something. Maybe one of those slices on the SSD happened to survive somehow?
Maybe the config is stored on the USB thumb at some point (e.g. when booting life and before choosing the "install" menu)? That might be an explanation: when doing a second install without re-writing the image onto the USB drive with dd, the interface assignment (which happens before the "install" menu can be chosen) might have survived on the USB drive. Although I am sure, I did the "dd" operation multiple times, I can not swaer that I did the "dd" before every installation attempt.