Hi cynwolf,
I haven't tried to repeat the process since then, as I managed to install OpenBSD on the machine in the meantime (at least in BIOS legacy mode). FreeBSD was just a detour. My premise was to avoid as much as possible any risks that could damage the OSX install on my macbook. I was attempting a USB to USB install: installer booted from USB pendrive with a second USB pendrive as the installation target.
What you describe sounds like the steps I outlined in my bullet-list above. The problem was, if I remember correctly, that immediately before the confirmation warning, there was a screen that showed all(!) devices and not just the one I had selected as an installation target. That's why I bailed out. I was afraid of any changes to the machine's main harddrive.
I probably should add that I have no FreeBSD experience whatsoever. Other than configuring an ad-hoc iscsi server by booting the FreeBSD installer from USB into the live system, no installation required. Which in itself is pretty cool.
