They don't actually have to enforce that though. Rather, it's a neat trick: if you do use encrypted chats, well, you're purposefully doing something illegal! To hide information, no less! That surely means you have more to hide, and since you've already broken a law, let's investigate further!
To be clear: I'm not saying this is the intended effect. But it is a frighteningly possible one. Anyone who has reason to hide their communication (regime critical activists, opposition politicians, investigative journalists,...) either have to
- accept that their communication will be scanned, making it trivial to spy on them and use that information (legally, no less!) to hinder/stop them, or
- do something illegal, giving pretext for hindering/stopping them since they've now committed a crime