While I don’t know what that means, I did read that when using whatsapp in a bloc where the government has control of the telecommunications, they can see who is messaging who by seeing someone sent and someone received a message at the exact same time. Probably is the same for other encrypted messaging apps. Reported in The Intercept.

There’s Beeper and bridges like Heisenbridge which could do this work but the crucial question here is why? The frontends you’re talking about help to obscure you from sites on the open web; there’s not going to be much of a benefit to adding another party into your chats, which are linked to your phone number.