bsdinstall does not have a "Recover config.xml" option like the previous installer
The new bsdinstall installer does not have an option to recover an existing config.xml from a previous installation.
The option would let the user select a disk, and then attempt to mount that disk and copy config.xml off there, and then use that config.xml for the installed system rather than the factory default. On the old bsdinstaller, this was unreliable, but did work under the correct conditions.
To me, I have it working for UFS and ZFS both.