I read that the destruction mechanism is explosives that rips open the fuel tank, internal to the rocket, but apparently then requires atmospheric pressure to collapse the rocket shell, and at the altitude it was initially at the pressure was insufficient to do that.

If this is really the mechanism then I suppose tough to test (at least expensive to have large enough low-pressure test chamber to blow stuff up in), but it does seem odd they wouldn't just have explosive charges to destroy the rocket shell as well.