It's actually the opposite; SS is more valuable on BRD because they have more abilities that are affected by SS, including empyreal arrow getting a cooldown reduction based on SS. MCH has less abilties and mechanics that benefit around SS (from the turrets to rapid fire). The entirty of their dps also comes from their own weaponskills, and not an auto attack or otherwise a source that isn't affected by SS. I'm a bit confused on how you came across this when you just acknowledged that MCH doesn't benefit a whole lot from SS.