I can't begin to tell what the GP post was trying to say. I will say this, however: Cars don't have emergency brakes these days. They have "parking brakes". Sure, you can try to use it in an emergency, but it's not for nothing that all references in the manuals and other documentation call it a "parking brake".
In the case of the 2004-2009 Prius, the pedal for the parking brake is hooked directly to a cable that goes straight to the rear drum brakes. That means it will work fine in an emergency, but remember, these are only the rears, and they're drums (except the touring edition). It still might work in many emergency situations, but I don't know if that's enough to stop a car that thinks you're flooring it.