Hello,
I has nothing to do with order type depended parameter.
in CO01 all order type will be displayed as per there order type defined in OPJH.
In case of process order COR1 all order type will be displayed as defined in CORN.
But in CO01 or COR1 if you enter plant and then try to select the order type then only the order type will be displayed as per the order type dependent parameters defined inside OPL8/COR4.
AAP is parameter for default order type for process order
Please refer OSS note 576556 - Process order creation: Order type default value
Best Reagrds,
R.Brahmankar