> This is in part because they were obviously too good for WebRTC native audio and instead gutted ffmpeg and compiled it to WebAssembly (I wish I was kidding but I'm not: https://webrtchacks.com/zoom-avoids-using-webrtc/).

Not a Zoom apologist I—I am also deeply creeped out by the fetish for covert data exfiltration in a platform that is so widely used in these quarantine days—but, as far as the tech goes, the story you linked seems to say that they do use WebRTC as of September 2019.