@londonfog I don’t specifically know the wipe function, but I might guess it would only wipe the target (defined) hard drive in the host configuration.
If you were ok with scripting it wouldn’t be that difficult to update the fog.wipe module to just loop through the disks instead of the one pointed to by getHardDisk function.
ref: https://github.com/FOGProject/fos/blob/master/Buildroot/board/FOG/FOS/rootfs_overlay/bin/fog.wipe
patching FOS is pretty simple to do too without needing to unpack and pack the inits.