Thr toothed washer is used to get more bite to be resistant to vibration, etc. there is no value besides convenience to using sem screws verse toothed washers.
I would be suspect of anything with sem screw with additional washer under it. That entirely defeats it’s purpose. The purpose of the teeth is to create extra friction between the bolt and the surface to resist rotation. A washer under that defeats it.
You would normally see these in pins in metal brackets like coil brackets… and sometimes used with plastics to get bite.
Just buy a box of #6, #8 star/tooth washers and call it a day.
