There are not many complaints about this problem on the Internet. I think just a few people used the Passphrase feature. But I think Opera should keep the feature because they had a breach in 2016 when the customer data had leaked to Internet. With the Passphrase enabled such unauthorized leaks are harmless. There is no way to tell if the cryptography does not have some backdoor for the government access but this is not a big concern, I am mostly concerned about potential unauthorized leaks. It did happen in the past, it can happen again.
I tried creating a new account from scratch and the problem is still there. So far, no mention of this issue in https://blogs.opera.com/desktop/changelog-for-96/