So the chassis is the ground is it? What happens when the day comes that a chassis is no longer metal? A chassis can not be ground UNLESS a ground wire is attached to it from the battery. Not too hard to understand.
According to MECP, I must have a certificate to be a installer. What about those of us that were trained 15 years before MECP was even in existence? MECP for the most part is doing this, you pay them, they do the Jedi Mind Trick to you, you get piece of paper that is totally worthless but looks good on a wall.
FYI, a good ground is not about the amount of metal in the return to the battery. It is about the combined resistance through it. With unibody cars that are a combination of glued together panels, crappy spot welds and blended metals, most of them are a horrible high resistance return to the battery. This is simple, electricity is an algebra equation, what you do to one side, you must do to the other. If you want to draw 100 amps of current and you have a build up of resistance on the ground, what do you think is going to happen to that amp in time? A good ground is one that is as low in return resistance as possible and is not always the chassis. If a amps manual also told you that jumping off of a bridge would not kill you, would you believe them and run out and do it or would you consider the fact that their info just might not be accurate?