That’s not sarcasm and it doesn’t allow any backup, it literally just to make sure you didn’t forget the PIN. It’s once a week, forever. It’s a good way to make sure people don’t activate 2FA.

https://faq.whatsapp.com/1278661612895630/

> WhatsApp will regularly ask you to enter your PIN as a reminder. As long as you don't reset the PIN, you will get a reminder once a week.