Brushed motor with shorted contacts can still rotate
When you spin a motor, it acts like a generator, now the force you have to put in is in relation to how much energy it produces, this big high wattage motor will have thick wiring, meaning low resistance, meaning low power when shorted. same for open circuit, it creates a high voltage, but almost no current. 

If you want to feel the braking force you need to have that generator drive a load that makes it generate some voltage as well as current, try a 10 ohm resistor,

for most motor drivers, the braking resistor is doing exactly this, loading the motor as well as it can, to slow it down as quickly as possible, however the amount of force is proportional to its speed, so it is less effective at low speeds.

To hold a motor at a specific position with almost not speed needs either servo feedback to correct it back to that position, or a mechanical stop to lock the shaft in place. 

For servo feedback, you do not have to use a servo motor, you could fit a hall effect sensor or similar to whichever motor you wish, as long as the controller has some feedback about the position,