The cheat VW used actually lowered engine performance and used more fuel to lower NOx emissions - that is why VW owners will not be happy with the new software, the cars will have lower performance AND use more fuel, so using more fuel will also make CO2 emissions higher.
The fact that Honda Accord Diesels had lower mpg probably meant the the NOx (seen as the new evil) were lower but CO2 may have been higher, but CO2 is now off the hook as the 'ultimate world destroyer' (which was probably something dreamed up by German Diesel makers anyway) and it now seems that instead of CO2 being suspected of killing people in 50 or 100 years time, NOx is actually killing people in real time today, every time a Diesel car drives past them, and a combination of Diesel 'black carbon' particulates and NOx cause smog and global warming worse than CO2.
The moral of this sad tale is, never let politicians decide anything technical, because they are normally accountants and lawyers and they just don't understand technical, common sense stuff - and will gladly take 'facts' from 'experts' - who are rarely unbiased inasmuch as 'someone' is funding them, and they often come up with the findings their paymasters want.