Disk 0 is not always a boot disk. In all my cases, disk 0 is always hard drive although I boot into WinPE via USB.
Rest assured different hardware does give different results, particularly there may be a difference with the way the boot is initiated, most recent firmwares allow to boot from USB pressing F12 (or similar), leaving device order "static", a number of older ones needed to access the BIOS and change device booting order, and to this you add that particular USB stick builds may remap disks, no, the risk of choosing the "wrong" disk in an automated script is "real".

Wonko