ProtonMail does not log things by default, but they can still be court ordered to do so by swiss authorities - if you want to run any business at all, you have to submit to a jurisdiction, you can only choose which one to run under. And even if your chosen authority is alright by itself, it can still be misled by other jurisdictions like the French did, using the terror-cudgel against climate activists.
I can also recall that in this case Proton said that had their user actually bothered to use any VPN, even Proton's, there wouldn't have been anything to give to authorities except for an exit node IP.