Emergency motor brake

We plan to use the MDC2460 controller on one of our prototype robots with brushed DC motors. We're working on the emergency stop/brake functionality for the motors.
Our design is based on the schematic found in the datasheet of the controller (figure 8 - image was attached to this post) and we have the following question:

* when activating the emergency button, do the motors continue to spin because of inertia, or will they be stopped almost instantly because the VMot power line is grounded? Not quite sure what happens internally, if the motor outputs are also grounded?

Our goal is to achieve a fast stop of the motors. What are our options?

Later edit: for anyone reading this and trying to find a similar solution. I ended up using the Dead Man switch functionality. At the same time the batteries are disconnected from the controller for safety reason. The robot stops in time.