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.
Fancy hearing me on an amateur podcast with friends gushing over one of my favourite games? https://youtu.be/1I7JfMMxhf8