I'd suggest designed on a last very unlike your feet is more likely the case. But I would guess quite close to the particular feet of the product testers. All feet are different so you can't get a product that fits every foot. For example, I really get on with Tevas, my wife doesn't. Our feet are different shapes.
I really don't see how you can give 9/10 comfort to something that doesn't fit...
I wear Tevas in 3 different sizes for different jobs (10 for leather "smart" sandals, 9 for serious walking and slumming sandals, 8 for paddling): shoe size, especially in sandals, doesn't mean quite as much as a lot of folk think...
