It seems reasonable to be concerned about a government that wants the power to reveal Internet users, but I couldn’t say on what basis Proton expects legal protection to continue after the move.
Neither of your links mention arrests, one specifically says "None of the suspects were detained". They don't seem to back up the original claim about Germany arresting the most people based on social media posts.
That’s an important distinction. Thank you for referring back to the original wording. They were investigated for violating the criminal code, searched, interrogated, and had devices seized in a number of cases, but seemingly not arrested.
as a german i can confirm that this happens very frequently (way more often than you think). usually it's politicians who file police reports which get prosecuted most of the time. i believe the last government (left wing coalition) built up massive infrastructure to prosecute such offenses. politicians in germany get special protection in terms of speech laws. §188 StGB allows the state to prosecute you severely, even without a private complaint from the politician in some cases.