SVPWM Zero Vector Braking?
The zero vector does not cause braking ... Initially.

The zero volt vector within SVM/SVPWM exists as a realisable state to synthesis the require voltage vector on a sector by sector basis. Whether 000 or 111 is chosen is an implementation concern.

So... Imagine the stator has current flowing. What is going to happen when all the switches are opened? The current is going to freewheel via the FWD and via the DClink - a negative volt loop. This causes the current to decay relatively fast 

What is going to happen if you turn on all UPPER or all LOWER switches? Is the current going to rapidly decay to zero and "brake" the rotor? No... It does nothing to actively decelerate the rotor (it will due to mechanical loading) , in fact because it creates a "zero volt loop" the current decays alot slower than if the classic negative volt loop is used (that which is used via SPWM). Likewise this is used for one PWM period before the next state in the SVPWM is used. 
This is equally used in soft-swiching of SR drives as it minimises current ripple due to the zero volt loop

So why is such a scheme referred to as "braking"? If you were to stay in this state rather than switching in and out of this state, the current in the stator will decay, the rate dependant on the RL time constant. Once this has occured you are now in a "braking" state as the changing magnetic field of the rotor-stator interaction induces a voltage which is now shorted out via the inverter. This permits a current to flow that will oppose the rotational force -> braking.

So in summary it depends on how long you are in this state, a very valid and useful state to motor-drives.