Protonmail has a feature called 'advance logging' which logs authentication to _all_ proton services
You might know they were forced to reveal the IP of a French climate change activist when they logged into their email.
Their CEO implied that had that activist used their VPN it would have protected them because "under swiss law VPN cannot be logged"
Yet in order to connect to their VPN service you need to authenticated to their services and when you do this your real IP is logged. I know this because in their emails service you can enabled advance security logging. This is probably the feature they implemented to catch that activists IP.
When you create a new proton mail account using TOR you must provide an email or phone number ( to prevent spam ) but basically there is no way to create an account anonymously.
Why not have the option to pay some monero to create your account as an anti-spam feature?
Its actually very difficult to use their services anonymously. You would need to use another VPN during account creation then only connect via TOR to their mail service.
Also keep in mind that your email address identifies your account. So if your email address is know by the authorities they can request they log when someone logs into the associated proton account. Using their VPN service will not protect your real IP despite the bullshit their CEO implies.
You basically need two accounts ( one for the paid VPN ) and a separate account for the email. That way a request to capture authentication attempts for the email account will not be logged when you log in and use their VPN service.
This feature was revealed to me in their sub reddit by another user, who one of the community mod harassed and deleted their comments.