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