I don't buy it either.
Been riding motorcycle for decades. The "load pipes saves lives" is total crap !!
It's a topic that can not be proven true or false either way. There is simply no way to know who "would have been heard" with loud exhaust..and was not, and got hit..and no way of knowing how many times a bike was heard and made someone look a second time and saw the bike. Someone said exhaust is ditectional..that is crap and that person has no idea what they are talking about. I know for certain that my bikes can be heard a minimum of 25' behind a car on the highway..probably further back on side roads. This most certainly should create a situation where a driver would look to see where the noise is coming from. Same concept as a siren on a cruiser or ambulance.