I have not tried for a very long time, I just tried to adb reboot fastboot on the one on 22.1 and got a variant of the menu I've never seen before
I can not remember what it used to fail with, maybe it was not until the flashing, OR something has been updated since last i tried....
On the one on stock the same command just reboots back into android. Booting into bootloader, it boots to android as soon as I attach a cable when in a direct port, but works fine in a port on the docking