B.L.E.

Reverse expo on the throttle channel is useful to make electrics throttle more like gas engines. Some ESCs have this function built in. The problem with electrics is that the rpm of the motor is too linear. Half throttle = half rpm = 1/4 thrust, quarter throttle = 1/4 full throttle rpm = 1/16 full throttle thrust etc. By using a reverse expo curve, the motor rpm is not linear but the resulting thrust is linear, or more nearly so.