I wouldn't be so quick to claim that "overinflated" is BS, given the numbers here. Every 10 degree increase in tire temp equals a pound of pressure. If they were cold-inflated to 50, you really have little idea what they were running, except higher than that by a good bit, which will depend on air temp, whether it was a front or rear wheel (drive tires run hotter), whether it was in bright (as in hot) sunlight, weight in the car, etc. It's entirely conceivable that these variables could add up to have made your running pressure near or even about 60 psi.
And is 50 even max cold inflation on those tires? I'm more used to seeing 44 or 48. Those numbers are there for a reason.
As for the blow pattern -- you're looking not simply at the results of whatever failure let the air out; you're looking at the results of the damage done to the tire while you got it whoa'd down and pulled over from 70 mph
. You don't know what the original failure looked like, other than that it *was* in the sidewall. (Tires with a nail hole in the main tread don't usually rip their sidewalls to shreds while you get them pulled over; there usually has to be damage to the sidewall first.)
So, yeah, maybe a manufacturing defect, can't rule that out. But Occam's Razor? I'd never run my tires at 50 psi. I've never owned a tire, including the stock Dunlops on my '07 HCH, that could cold-inflate that high. I know a lot of people on this board do it anyway; and I've come to accept that if it didn't *usually* work, we'd hear a lot more about failures than we do. But "usually" ain't "always." Sounds to me like we've got an unfortunate "not usually" here.