Currently, all phone calls made over a cellular network are monophonic, meaning audio is compressed into a single channel
This bit from the article is what I am trying to convey. Teamspeak doesn't use whatever phones use when you make a phone call, even if it's a cell phone. Cell phones do not have to do this. They have the bandwidth for stereo phone calls and yet, so far, they still compress it into garbage unless you're using a VOIP app or Wifi calling on both ends.