> To be useful, we would need a large, unbiased sample.  Lacking
> that, I prefer to follow VW's recommendations, since they have made a
> scientific study of the issue.

It is incorrect to assume Volkswagon has done any kind of study, scientific
or otherwise, without tangible evidence of same.
Just because they design and build a vehicle for availability to the mass
market, they are not bound to 'study' anything about ANY part of the
vehicle, tires or otherwise.
It's just that sort of blind faith that causes consumers to believe myth
over real 'fact'.  IE; VW -a multi billion DM company doing business in
hundreds of countries throughout the World- builds a car so it HAS to be
safe to own and drive.
[Lessee, saddle fuel tanks in Chevy pickups and Pinto gas tanks come to mind
here...]  And both those manufacturers are way bigger than VW.  Where were
all their scientific studies??

If I was to hazzard a guess, and that's all it is, VW probably inquires from
the manufacturers what tires they would recommend for a particular
application.  Then they go the extra step to find out how little they'll
have to pay for the tire on the xx,xxx units they intend to build and sell
that year.  Come next year, they start the process all over again.
They'd rely on the tire manufacturer for the science, then do the correct
bean counter thing and buy it (sic; recommend them) on the cheap.