I've got the original English edition (goes with third edition Settlers), not the most recent. Under section 5, "Commodities," the rulebook goes out of its way to distinguish commodities from resources: "You may exchange 4 of the same commodity for 1 of any resource or commodity," "Some progress cards specifically mention 'resources' or 'commodities.' These cards can only effect [sic] the type of raw material they specifically mention."IIRC, that's the jist of what Mayfair 3rd edit. rules say. One specific example I remember is the tech tree that lets you trade 2 of the same commodity with the bank for one of any resource..... there was mention that commodity means commmodity, NOT resource like sheep, wood, etc.
It doesn't specifically say you can't use commodities as their corresponding resources for building, but it's implied pretty strongly since you can't do that for trading. Nowhere does it say or imply that you can use commodities as their corresponding resources for building.
I don't know what the most recent rules say.