I assumed 100% correct and the statement on the thing is still not untrue. It just so happens that if you buy the game with vouchers then you get no points to double because you've already gotten points for the purchase of the vouchers, they're not going to award points twice for the same single transaction of cash.
No, you assumed terribly wrong because you're very stubborn and very arrogant.
You said "double coins by purchasing", while the text only says "get double the coins". Not by purchasing. Which, combined with the whole voucher thing, can lead people to think that they will get extra coins if Link's Awakening is one of their redeemed games.
But whathever. This thing of yours is getting very old by now. I'll leave it here.