Hi Chris,
if the QM-order type/plant is not assigned to an actual costing variant (T-code S_ALR_87004665) where the incorporated valuation variant does not contain a costing sheet (Check this using T-Code OPL1), no actual MOH is calculated no matter what the user is ticking.
Instead of manipulating the selection screen of CO43 check your QM-order type settings, looks like there is some space for improvement ;-)
BR Christian