I gotta say, I really don't believe for a second that GP4000s have some sort of inate and consistent design flaw that causes them to randomly and catastrophically fail more often than other tires of similar construction. They're about the most common and appreciated go fast tire available on the market.
What I find MUCH more likely is that because the GP4000 is the most common go fast tire out there...sometimes when someone has a sidewall issue of any kind, it goes up on the internet as some grand conspiracy theory. Just like when sidewalls blow out on other tires. Except, there are a lot MORE GP4000s in circulation, so you get more conspiracy theory stories online, and it is that absolute number people refer to when they claim "theres something up with these sidewalls OMG!!!"
Occams Razor. Simplest answer is probably the right one. And, the simplest answer is most definitely NOT some weird, yet unresearched and unknown design flaw that mysteriously make SOME peoples GP4000s catastrophically flimsy, while others go thousands of miles.
The simple answer is there are a LOT of these tires on the road, so you have correspondingly more failures.