How many coins do you get when purchasing any game with a voucher? It's 0 what is 0x2? Even on a literal level the statement advertised is 100% accurate, heck they could say it was 1000x the normal coins when bought this way.
It doesn't look great if you are expecting coins obviously I do see what you're getting at but you definitely couldn't call it false advertising, it's just a shame they've picked the Links Awakening pic from the eshop where you do get the double 300 coins with the purchase, but yeah, 2x0=0 they're not lying in the advert.
But if you look at the picture, it looks like they are saying that you're getting points for Link's Awakening. Maybe in this particular deal, you ACTUALLY get coins if Link's Awakening is one of the redeemed games. Although it's not the case, the advert seems to suggest that much.