I like a good conspiracy theory as much as the next guy, particularly when it involves the manufacturer of my craptacular 1980 Pontiac that turned me off American cars for over 30 years.
That said, it's hard to be sure of how widespread defective driveshafts really are, given how many of these trucks are sold every year. At these sales volumes it only takes a 0.1% defect rate to create a huge uproar in the forums. And then there are the cases like mine, where a tire swap or other "quick fix" did in fact solve the problem. GM was right to suggest it as a first line of attack.
Anyway, I hope the more seriously afflicted owners do find a cure. Big corporations are driven by economics, always seeking the cheapest possible way around a problem. The trick is to make it unbearably expensive for them to ignore you.