[Quoth]

Almost a week!
I have come to a conclusion on reading the website, not playstore, T&C of Google Accounts, which are not just for the playstore:

1) These are separate from a google login name.
2) Unless there is a payment method setup (with real name, address, phone, email and paypal/debit/credit/card it's not setup.
3) If it's closed (i.e. there are no payment methods), A gift card is not accepted, though the 'account' still works for all free Google services.
4) You can add it in the Playstore but have to go to website in Browser to remove it. It's not fully removed, because it will still be live in PayPal, so you have to also contact PayPal customer support to fully remove it. I don't know about credit/debit cards.
5) Despite "EU right to be forgotten" they keep the real name, address and phone number on file, though it's hard to find it.

Final conclusion: Do not ever buy or accept a Google Play Store Gift card if you don't have a currently working payment method. The store you bought it from is unlikely to refund you. Even if you do have a working payment method the Gift Card still may not redeem.