Bill of Material Base Quantity Unit of Measure

When creating a Bill of Material (a.k.a., BOM) the default Base Quantity Unit of Measure (a.k.a., UoM) is the base unit of measure of the material master record for that parent material. This defaults in and cannot be changed, unless a potency/product unit is defined in that material master record (a.k.a., MMR), THEN it permits ANY UoM, alternate or base, to be entered into the Base Quantity UoM field (RC29K-BMEIN). The default will still be the MMR base or whatever value is entered into the goods issue field on the material master record, work scheduling (or other places too) view.

Is this truly the only way to get a different Base Quantity UoM for any BOM? What if you were not using PI functionality? Why wouldn't any defined alternate UoM be permitted?

I recognize the UoM of the Recipe header can be different (not the BOM / Material List within the recipe - the actual recipe header quantity only) without all this potency/product unit setup.

Do not confuse this question with the item/components ON the BOM, I'm just refering to the header material and the Base UoM for the BOM.

Your comments and input will be welcome.