All those things you listed simply confirm that a particular person bought a Mullvad scratch card. There’s literally no way to associate that data with a particular Mullvad account. To do that they’d have to have a record of the card batch number and somehow have accessed the code underneath the scratch-off panel.

You’re not wrong, BUT that’s why Mullvad offers other forms of anonymous payment, the flexibility lets you be as paranoid as YOU want to be. You can pay in Bitcoin, or you can literally mail them an envelope of cash with no return address. Amazon scratch cards are just the most convenient option, and as always, you trade security for convenience.