Restoshaman raid heal BIB and Gear Check at odds

So when I do best in bags its recommending mastery gems and enchants and if I do Gear check its recommending crit in those areas. The difference according to the robot is .30% from what I have set up which is the BiB recommendations, so its not a huge disparity. But why does this disparity exist at all?

In the Best in Bag settings we have a “threshold” for gems/enchants that defaults to 0.5%. In the gear check we don’t have that. You can get different results if you don’t set the threshold to none on BiB.