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.
"Double coins by purchasing"
"Get double the coins"
What possibly difference do you see on those two statements when it comes to getting something like this? If a sign in a store said "50% extra free" would you look at it and not understand that you have to purchase the item because the word purchase isn't included in the statement? In instances like that the purchase aspect of the offer is implicitly implied, the statement of such an offer on a product in a store(front) only applies to those who intend to purchase it.
Again, you get the points for the vouchers when you buy them and it's part of their Ts&Cs that you do not then get points when you redeem them for a game on the store as that would be rewarding points twice for the same money being spent.
But as you say... Whathever [sic] You think I'm being arrogant in pointing out that there is nothing untrue about the statement being made there. I think from the confusion you have about my being "terribly wrong" with my ability to discern the meaning of a statement made in a foreign language simply from the how and where it's being used to your inability to understand the statement in (presumably) your home language or the confusion which happens when you multiply any amount by zero I don't think there is much gained from this other than you thinking I'm stubborn for not agreeing with you that Nintendo should give you 300 extra points for your voucher being spent which you already got the points for.
Again from the Terms of the vouchers that I'm guessing you didn't read.
"The Nintendo Switch Game Vouchers may not be combined with any other sale, discount, or promotional offer unless otherwise specified."
So even if the vouchers would reward points when they're redeemed they wouldn't ever work with the promotional offer of x2 points unless it was specified that they would explicitly.