Proton doesn't provide public APIs for retrieving the public GPG keys associated with their users' accounts, nor do they provide a way to send encrypted mail to their users' accounts without using their official apps.
Ergo, Proton is not really working to further the state of cryptography for email, they're only working to compel users to use their proprietary software (and ultimately their paid services).
If services which do automated sending of emails to their subscribers/users have no way to encrypt those emails for its users who are on proton mail, I don't understand how Proton can claim to care about encryption.