Proof of what? That they are a profit based company that engages in security theatre marketing to sell their service. This is self evident. I find Protards especially suspicious when they can't accept this basic fact.
Every single email provider from Switzerland has to follow the law. Pretending their service has something over other services when they just follow the law is kind of ridiculous. This is marketing and it sucks.
Companies sell images and Proton, being a major corporation, is no different. People think throwing money is going to solve their problem and Proton is happy to stroke this feeling to make profit.
For me, I liken it to advertising your company is bonded. In California they have recognized that this is a deceptive marketing practice and made it illegal for businesses to do it. If Proton just advertised we follow swiss law like every email provider in this country it would be accurate. Instead they create security theatre to attract users.
A great example of this is their recent credit card scandal where it was revealed that they they store meta data on transactions needlessly. They claim privacy, but yet they store your private information on their servers. They don't disclose this actively and it is a serious violation of privacy.
Proton's answer is always the same lame garbage along the lines that anonymity is not privacy and then they try to explain how you can protect yourself. The truth is their service does not respect privacy in some regards. You point out their technology is pretty solid. Sure, but that is not my issue with them.
My issue is they pretend to be all about privacy, but then they store your personal information and it is YOUR fault. Like the end user is supposed to magically know they do this and somehow protect themselves when the problem is with Proton itself.