The rad caps on the S/T vehicles don't cause the problem, they make it worse. The problem occurs when the dexcool becomes contaminated. For the most part, people have pretty good luck with it, if they flush it every 3 years at less than 50,000 miles.
I currently use green antifreeze in my vehicles after having major dexcool problems in my Impala. My Impala doesn't have a cap on the radiator either, it has a pressurized reservoir. The problems occured less than a year after a flush and refill. My car is meticulously maintained, all levels are always checked regularly.
I'm sure that this thread will be full of suspected causes, half truths and conspiracy theories, but the bottom line, IMO, is any product that can be tainted so easily, and become destructive to so many expensive componets should not be used. Dexcool has the potential to be superior to the standard green antifreeze, but at this time, it is not refined enough to be used in mass production.