You can disable an account without knowing who owns it, although they do have credit card/payment information now, and I don't think new accounts get encryption services unless they pay.

That said, if your inbox is encrypted, protonmail does so on the client side with a second password. They can maybe delete the account, but proton mail doesn't know what the encrypted data is. What happens to new emails sent to a disabled address is anyone's guess though. Honestly I think they're doing the best they can given the circumstances