That hailing was mostly done by diesel advocates, I think. The problem is more particulates in the exhaust, and the fact that it's hard to just make lots of particulate matter vanish into thin air, so to speak. The "burnoff" approach that VW used to use was maybe the best way, although urea injection also works. You just have to keep refilling a urea tank. And no, urine doesn't work just as well.
I'm sure that the diesel advocates were all over it (maybe that includes me). But I also remember seeing those figures in some rather reliable sources (e.g. World Book Encyclopedia).
Also not that the urea injection isn't for particulate matter. Now these are the big two emissions that diesels are known for, particulate matter and oxides of nitrogen.
Particulate matter wasn't regulated for years even after regulations for stricter for HC, CO and NOx emissions. I guess they didn't see it as poisonous as the other emissions. However once they started regulating PM (around 2010 for commercial diesels, at least in Colorado) they were mostly done away with by simply adding on an active or passive particulate filter and incineration system. Active particulate incineration means periodically spraying fuel into the particulate filter to heat it up and incinerate the PM before the filter clogs. On long haul diesels the particulate filter receives enough heat from the engine running all day long to incinerate the PM. With such systems PM is no longer a problem, and as far so know wasn't any part of the reason VW got into trouble.
The main problem with modern diesel engines is no longer the PM but the NOx emissions. That's where urea injection comes in.
It used to be that diesels naturally got better NOx emissions than gasoline engines. This is because gasoline had to burn close to its stoichiometric air/fuel ratio (many times going lean as carburetors weren't precise), which is quite hot, whereas diesels normally run far from stoichiometric in a super lean phase running lots of cool air through the cylinders which keeps overall combustion temps cool. The excess of oxygen also has always made diesels produce far less CO and HC emissions. But then the EGR system was invented for the gasoline engine along with precise fuel injection. Such systems have allowed NOx emissions to be largely reduced in gasoline engines. But they don't work a well on diesel engines because diesel engines don't run well close to stoichiometric nor do they run well with EGR.
In conclusion, the main emissions hurdle for modern diesels isn't the typical black cloud of particulate matter. It's the difficult to control NOx emissions. But that doesn't mean that it can't be done, and I hope the scientists can get this figured out for small diesel engines.
I get upwards of 55mpg going 75mph in my 1985 VW diesel, sometimes over 60mpg if I'm careful with the pedal. I kind of think something must be wrong with technology in the sense that very few cars can attain that kind of fuel mileage today.