It's not bad advice at all. It's the truth. It would go something like this.
Motorcycle rider signals right hand turn to indicate a lane change.
Driver behind him has no idea what that means and ignores it and proceeds to make lane change as well to pass rider hastily.
Motorcycle rider starts his lane change and crash!!
The drivers excuse will be, he didn't signal, it's that simple.
It may seem like I'm against hand signals; I'm really not. It's the fact that drivers lack the education that makes hand signals relevant. Using hand signals that majority of drivers don't know is dangerous to riders.