Exactly. Its a de-lamination of the tire tread off the casing. And they don't usually even have a tire pressure drop when it happens! It sucks really bad, but the poor truckers have no clue.
The blame, if you want to put it on someone, is the poor job of the tire retreader. A good retread should be just like stock, since it is vulcanized rubber and thus should become one with the tire casing. But if the tire isn't cleaned right, or if it is a bad casing, or if 100's of other variables aren't met, then the tire won't hold up long-term. Again, not the trucker's fault, but the tire guy's....and a lot of Murphy's law and bad luck, too.