On a high traction surface that sounds reasonable, up to the exponential point. What would cause that?
It's all about the load you put on the motor. With significant gear disadvantage (rollouts greater then 1:1), the motor has to create more torque through it's entire power band then it would otherwise with less gear disadvantage (Rollouts closer to 1:1).
Voltage makes RPM, Amps make Torque.
IēR tell us that (Ampsē)*Resistance = Watts dissipated as heat. This is where the exponential comes from.
Your motor has a massively low on resistance. In the area of 0.01 ohms and lower. Obviously this will be different from motor to motor, this number is just an example.
But if that 3674-Canned 2-Pole is pulling 120A, it's putting out (for example) 144 watts of heat. That's a lot!
But if gearing it down means you pull 80A, that's only 64 watts of heat.
This is why overgearing is so incredibly bad for electric motors.