Wow 1200 miles! so I suppose if you went out and bought something that didn't come up to your expectations you would go out and buy the same again!!?True. But it doesn't identify it as a Scwhalbe production issue either. Any tyre can suffer damage through fair wear and tear or accidental damage during it's lifetime.
The explanation I suppose is that it's quite possible, as with the misfortune of experiencing a puncture, that you've just been unlucky. Otherwise there'd be more reports of this type of thing being reported I reckon. But not so unlucky that the tyre hasn't given you 1200 miles of good, safe use thus far.