"forearm in a odd angle" Huh? The wrist does the twisting. Adjusting your grip is about as difficult as using a fork.
The only thumb throttle I ever used on a non-ebike was on a 3 wheeler ATV. I think they got banned.
What do most motorcycles-mopeds-scooters have?
Unintended throttle twisting is dangerous. Some clever people might maybe someday get that fixed. Seat switch, weight sensor, etc.
If they are using PID control, they could limit the D.
I call dibs on the patent!