Using it when you place a pre-order is YMMV, that's an established fact, as the coupon code has to be used when you pick up the game, not when you make the pre-order. If you get the 10% off on the pre-order, then you're lucky.
It works without any issue when picking up a pre-order, as I've done with Bioshock LE, Dewy's Adventure and Eternal Sonata, as you're using it when you're buying something. When you pre-order something, you're not buying anything.