Depending on the SKUs of parts used, a single product (say MacBook pro 128GB ) may have multiple SKUs, i.e. versions of the underlying board, to accommodate for

Depending on the SKUs of parts used, a single product (say MacBook pro 128GB ) may have multiple SKUs, i.e. versions of the underlying board, to accommodate for different parts and their dependencies. If you're under the assumption that Apple and Co don't spend the effort in abstracting out dependencies on their hardware, your deeply mistaken. A significant portion of engineering in hardware circles is spent in this effort