iivvoo It is important to distinguish the joint account and joint membership (new) from each other. You and your wife can still have a joint bank account (both names on the bank account) with your seperate bunq user accounts. This has been possible for more than a year.
Joint accounts replaced a previous feature known as connect where one person would be the owner and others would get access to the account.
So, without changing your current membership (Premium or Pack) you can still have a legally joint bank account, with both of your names on the bank account (IBAN), by simply adding another bank account (bottom of the account tab) and choosing joint.