If someone legitimately cares what email provider you use and uses that against you in the hiring process, chances are it’s not a place you’d want to work anyway.

It was the company’s official stance per their official social media account. Not just the CEO/one board member.

I largely agree with what you’re saying, except the official Proton Mastadon account doubled down on that personal opinion. That seems pretty clear that it’s endorsed not just by that one individual on the board.