[Al Skierkiewicz]

Danny,
Yes you have been lucky, very lucky, for a variety of reasons. One, the safety issue of having battery voltage present on clips allows the potential for shorting the clips together with no fuse/breaker and a battery capable of welding the clips together if they should touch. At that point, the wire on the clips turns incandescent as 600 amps begins to flow. If you are lucky to be able to drop them before injury occurs, the smell of burning plastic will permeate the room, your clothes and other materials close by.
While it is true that pushing the robot does back feed voltage through the output devices, it is not a good idea. When pushing the robot, you have to get the robot moving at least as fast as it travels at full throttle to match the battery voltage you are trying to apply. Using a 7.2 volt battery helps some. However, think what might happen if someone clips the battery in while the main robot power is still applied and gets it backwards.
A good rule of thumb is to test a device as it will be used. In this case with battery connected and commanded by your DS. We have the students check each other's work as the robot is wired, then check it again when complete, then a mentor checks it. Then we apply power with all breakers removed and start adding them one by one looking for problems, no power indication on the device under test or smoke. With this method if something is wired wrong, only one device will give it's life for it's brothers and sisters.