My local Yamaha dealer tried to explain why SHOs, don't have vented props, something about the SHO senses the unvented prop and advances the timing to aid in hole shot. I asked why Mercury 4 strokes still have vents. I was told Mercury makes horsepower with RPMs and the vented prop allows for the prop to spin up faster allowing adequate hole shot for a Mercury. Yamaha has more torque, so vent holes not needed.

Can someone better explain this to me or is this correct?