I think the idea is that what you are getting from Amazon is a card with a code on it. Amazon doesn't know which code it's sending you, you just get one at ran

I think the idea is that what you are getting from Amazon is a card with a code on it. Amazon doesn't know which code it's sending you, you just get one at random. Mullvad likewise doesn't know which code Amazon sold you. So you get your card, enter the code into Mullvad, and none of that information is trackable to you. Amazon would know you bought a Mullvad card but would have zero way to link you to a specific code. Mullvad might know the code was purchased from Amazon, but not who was the purchaser. Worst case scenario is that Amazon rats you out to the police/CIA/NSA/etc and now you are on a list of people that purchased Mullvad VPN services.