It's complicated. think about what happens when somebody uploads sex trafficking content via the app. If the app, when installed via a marketplace like F-Droid, doesn't actively forbid such behavior, whoever ships the app might be liable for "helping" them in some jurisdictions. So, right now, Amethyst includes statements to protect us against it and F-Droid claims those statements make the app not FOSS (I disagree).
Discussion
I see your point.
The app developer can be liable if someone uses it to transmit illicit content? I’ve never heard of the developer of a web browser or SFTP client being sued for that.