I mentioned earlier in the thread, I had two GS engines replaced for corrosion on my WC's, one GS and one GSA with the black engine. I also had another engine replaced, along with a host of other parts including wheel and swing arm on a WC 1200 RT I Had, I will see if the old thread is around. None of them had yet seen a winter, and I am an anally retentive cleaner. Your point is totally valid, but from my personal experience, BMW have been one of the worst offenders. I have a mate down south who's GS Rallye looks like it was raised from the wreck of the titanic.
Manufacturers should do better, paint should be better, but warranty and how it's backed up counts for a lot to (IMHO) My V7 is mint, but no garage queen, used year round for about 15 months now, and no corrosion, save for a couple of fasteners I've replaced.
So, I'm not disagreeing with you as such, but it's something that is present over the whole spectrum of modern bikes, and Ding Dong is not so much facing a corrosion issue, but a dealer that's tried to feck him over and take him for a mug (IMHO)