How is this at all surprising? Any non-open source program can do everything you just listen and more. Discord may have been dumb for naming their analytics request point "/track" but that doesn't make them worse than anyone else. I wouldn't be surprised if Word sent every button press to Microsoft. And besides, all the chat data is stored on their servers anyways, so it's not like they get a whole bunch of new data through this.
But in particular the problem is that it's web crap and it pulls down it's code every time you run it. And now with the websocket backdoor it doesn't even have to do that. This is very different from a compiled program.
It's not surprising but it is also not acceptable. I chose not to use it and encourage others to avoid it.
I wish people would stop touting this. Just because you pay for it doesn't mean you aren't being tracked. I would say MS Word is considerably worse because you have to pay for it and it still tracks you.