But what is truly, truly, astounding is why they wouldn't just hook up the damn existing "yieldfrombuildings"/"yieldfromterrain"/etc functions that were already being used by the original 4 yields (science/food/production/gold).
They even went so far as to create new columns in the Buildings table for % yield modifiers for culture (and did not bother to implement any equivalent functionality for Faith... i.e. %Faith bonus for the empire, or %Faith bonus for the city).