Fixed, and it was two bugs, not one. Your throttle was on a trigger and the
game was treating triggers as buttons, so it could never be bound. That is
fixed for every controller now, not just yours.
While checking it I also found that RC pilots who never bound a fire switch
could not shoot at all, which would have been your next complaint. Fire now
works on the mouse too until you bind a switch.
Update is live. Controls > Calibrate RC Transmitter, adopt your Pocket if it
still shows as a gamepad, then run the stick calibration. Your throttle will
show up this time.
Thanks for the report, the "seen as a button" detail is what cracked it.
Source: Steam Community (opens in a new tab)