Guy:

I don't like electric handbrakes, but it's nothing to do with tracks, racing or history, it's just that it's another piece of electrickery that can go wrong.

 

One potential problem with an electronic parking brake on a car that is tracked is the parking brake pads may fuse to the parking brake if the electronic parking brake is automatically set when the car is placed into park.  

Perhaps Porsche is fitting an override to avoid this problem.  

Another problem is the difficulty in changing the rear brake pads as a command must be issued to the controller to retract the engaged parking brake pads away from the brake surface.  While it is not a major problem, it remains an inconvenience, especially in the field.