The point I'm making is that accidents do happen and Schwalbe is obviously a very good make of tyre.
If you were showing us a brand new tyre then you might have a point. But you weren't, so you don't. It's a minor bit of frayed wear on a tyre that has 1200 miles on the clock. A well used one, that you've conceded, may have been accidentally damaged by yourself at some point. You've had no punctures in that time. The tyre's still fit for purpose.
The manufactures don't seemed concerned by it. So, on a personal note, I'd be content with their response. Obviously you're not John. Why don't you do as they suggest and take it back to the retailer?