If one gives the architect the benefit of the doubt, then there appears to be a desire to include in the plans "something for radon" he/she knows should be there. This suggests another angle from which to approach the problem:
Clearly the architect thought he or she learned somewhere that "typical 2-inch radon pipe" was what was called for. Perhaps this is an honest if well-intentioned mistake. Therefore, perhaps some outreach to the American Institute of Architects (AIA) regarding education on key features of good RRNC might be a way to get conscientious architects to include RRNC properly into building plans. Then if this feature is already shown correctly (i.e., the right size, materials, location, etc.) directly on the plans, would builders be more likely to follow that?
(Of course, I still agree that the best way to get RRNC installed correctly is to require professional certified radon tradespeople to do it.)