The link you gave is just a personal opinion of some dude, he even admits that. No statistics, even lying, is provided.

I can easily throw an opposite opinion: besides riding motorcycle every single day, I drive car, and usually I notice motorcycles roar too late. Also, I had two occasions when drivers didn't notice sound of my motorbike (it's not quiet at all) and changed lanes right into me. So I prefer to assume every driver is deaf and ride that way.