In my anecdotal experience, as the owner of both noisy and quiet motorcycles, there is very little truth to that. My noisy motorcycles have just as many "Sorry mate, I didn't see you" incidents as my quiet ones. On the other hand, looking like you might be an evil baby-eating biker (cruiser-style bike, black leather, open face helmet with a beard and sunglasses, blatantly disregarding road rules) does seem to have a probably statistically significant reduction in other road users treating you badly. People don't "not see you" or "not hear you" they judge you as not being a danger to them - perhaps subconsciously, perhaps consciously, but I have strong suspicion that lots of people do look and see you, but their heads categorise you as either "just a tiny fucking motorcycle, I'm insured so I don't care if they bounce off my car" or "I'd better not annoy _that_ guy, he might reach through my window and rip my head off and then go home and murder my family and pets".
I could _maybe_ see an argument that especially quiet vehicles (electric for sure, but a lot of modern ice cars as well) might improve pedestrian safety with a little bit of "fake engine noise" being projected at low speeds where pedestrians are likely to be around, but 105db straight through pipes do not improve anyone's safety at 25mph+ in my experience, they just annoy people. (And I say that somewhat hypocritically, as the owner of a Ducati with aftermarket and louder than stock pipes, but which fall a long way short of 100+db straight through Harley Davidson pipes.)