I bet you would find it even nicer if reverse applies the brake!! I dont really see it shutting down as a bonus, unless of course something like what happened to you happens!
To shut the car down when you hit reverse means you have the idle stop screw wound out too far, therefore closing the carb all the way when applying the brake, the idle stop screw is there to set the idle so you can apply the brakes without the car stalling all the time.
To shut the car down the quickest way is to put you finger over the exhaust pipe opening (careful can be hot) or squeeze the fuel tubing, (safer but takes longer).