It doesn't really work like that.

If it is against their rules, why Amazon allows their partners to sell gift cards to companies to then be sold? I repeat it's not an issue with Bitpay.
The companies do not buy the gift cards, they use an API. Even some neobanks and assurances (yes) sell gift cards. There are also thousands of rewarding sites using Amazon vouchers to reward their members.

I could also give the example of someone who posted here some months ago with the exact same problem after purchasing a gift card from Bitrefill.
Even Bitrefill warns people on its website with a message saying something like "Avoid using a gift card with an account without a debit card added or a brand new account".

If you google you will find so many stories with people suspended after using a voucher or a VCC on Amazon