Hehe yes it's true that they could have a material which simply flexed at amazingly high loadings, and they happened to have a wing design that generates so much more downforce than any other team. But I don't buy it - other teams are more than capable of copying a part as visible as the front wing, and if the Red Bull wing (and all iterations of it last year as well) was so much more effective then we'd be seeing the flexing on more teams.
A more reasonable explanation is that the wing layout etc. doesn't by itself produce significantly higher loading than other teams designs, but by allowing it to flex cleverly they bring it lower, which then generates many aero benefits including even more downforce.