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The lobe being vertical isn't that rare, as there's four pairs of them per camshaft, making for eight positions per rotation of the camshafts where there are vertical lobes, not one. Pictures of the old chain design versus new show that the new is less likely to stretch, so obviously that was what they determined to be the effect, though I'm not so sure they really know what causes some chains to stretch, just that they do.
The design of the tensioner has changed too, so that's part of the problem. It seems what happens is that when the chain stretches enough and the tensioner is no longer able to provide enough tension the chain can wobble enough to damage the guide, which allows more wobble, which damages the guide even more, and the snowballing effect eventually causes the chain to break.
If the damage occurs when the engine is cold then start-stop doesn't explain it, because the ASS doesn't work with a cold engine.
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