They are probably just making it available at the convention in the same way they have previously sold retail items at the comic-con store. I'm sure a lot of people have not heard these things were going to be produced.
The thing I find odd is that I don't remember them announcing any retail-available product with the exclusives before. The question has been answered, though, over in the Matty forums...
It is being sold at SDCC. It is not an SDCC exclusive. Any other order or pre-orders you have with other sites will not be cancelled as a result of it being sold at Comic Con.