Even in pure EGR designs like Isuzu the real life emissions are not far from the lab. BMW, Daimler, etc have all managed emissions in real life which correspond to real life reasonably well (less than 3 times difference). There is only one other manufacturer which has an order of magnitude difference between lab and road.
I am going to venture a guess why. This is a natural result of a company which has elevated Branding to and above the level of Engineering in a business that is by its nature engineering driven. VW is the only car company which has an EVP solely in charge of branding and at the same (or higher) level as the director of engineering.
It is also a company which does not follow the best R&D practices where you develop something, push it out in small quantities to a particular (and usually well known) pilot brand and promote to your main stock only if it works in the field. It originally set-up Skoda/Audi this way and by sequential orders of Branding and Marketing over the years rolled back that division to the point where VW separates solely on the basis of what trim and how plasticy is your car trim. There is _NO_ pilot series and no natural "promotion to mass manufacturing" any more. Branding and Marketing also put the stake through the original idea of Skoda being the testbed for new tech from 12 years ago (that lasted as long as Fabia Mk1 and Octavia Mk1).
As a result, any major changes as needed for example to comply with new emissions regs, end up as extremely high risk as they are not tested properly in small series on the road first. This, in addition to shiny-shiny being given higher priority than actual engineering results in a natural tendency to cheat. Nothing surprising here.