If I remember correctly, suppression is just suppression*bullets fired (bullets fired = rate of fire * burst length). Doesn't matter if they hit, so accuracy doesn't do anything for it. However, there are additional suppression modifiers in the cover tables, 0.5 for light and 0.1 for heavy cover.
But if thats the case, why are there so diffrent outcomes in the time the mg needs to surpress? Only because of occasional yellow cover? Hmm.