Over the years this has also been a major source of contention for me. Line tapped? You're ALREADY f*cked, hard. No, slang isn't going to fool anyone, especially because you're sure as heck not going to be taking your low level dealing case to jury trial to make some ridiculous argument that whatever clever lingo you used didn't refer to the drugs the CI/UC bought from you or was seized in the search. And even one slipup like 'yo not on the phone' removes that last shred of doubt.
Oh and text messages? They're stored indefinitely while voice convos need an active tap at the time of the convo.
The worst part is, I *always* explain that if they're interested in real security for their communications, I'd love to set it up. Never any interest besides actual friends who then proceed to use secure channels with me only, which obviously won't help. Reality is it's hard, especially if you want to defend against a federal level investigation. Staying out of jail starts long before a tap is requested and requires physical security practices that are way more important than the digital practices.
Still never had a dealer that doesn't talk openly/obvious obfuscation and text over plain SMS, no matter how many rants about security I go on about.