If it is just a bug, then we should expect a quick fix and firmware release from VW. If, however, it was a conspiracy, and there is no way that VW EGR technology can ever be made to pass the NOx requirements (without additional hardware - AdBlu tanks), then VW is screwed.
My point is that a "too good to be true" bug could easily have quite devastating consequences if it's just fixed. If they remove 'false' in the putative "if (isInTest() || (isNOxReductionNeeded() && false) enableEGR();" line and this increases fuel consumption or reduces maximum torque a lot, they cannot simply release that fix.
Embedded automotive control systems and scientific research are quite different domains, but in science I've repeatedly been close to thinking I had solved a problem, just to realize that my benchmark was off and the code was not really working at all. I have not published any of those results (AFAIK) yet, but I've reviewed and seen publications with blatant errors. When you have reached the kind of result you hoped for and believed likely, you are not on guard anymore. Fixing the blatant error might very well mean that the whole work is pointless. The error is trivial, the consequences are not.