Sure they do. Each airline has different alignments of booking class to fare type (eg Economy lowest, low, flex) and there’s a hell of a lot more of MH codes in the lowest pile compared to BA.
BA puts almost all QF fare classes is Econ Lowest, nothing in low, only YBH in flex.
This is the same method QF uses. It doesn’t explicitly discriminate via carrier (other than QF itself)
