Removing it should remove the records.

"You can provide an external email address for notification or password recovery purposes. Should you choose to provide it, we associate this email address with your Account (for password recovery or notification purposes). Such data will only be used to contact you with important notifications about the Services, to send you information related to security, to verify your account or to send you password recovery links if you enable the option. We may also inform you about Proton products in which you might have an interest. The legal basis for processing is consent and you are free to modify this in your Account settings panel at any time."

https://proton.me/legal/privacy

They mention nowhere that they keep older records. Typically the things that they can see are things they either cannot encrypt for technical reasons or if it is something you chose them to store (like Login history logs for example).