That can‘t be why – one benefit of their weird way of using WebRTC is that it would actually allow them to provide end to end encryption in all browsers, regardless of support for WebRTC insertable streams.
Zoom does very weird things in the browser. They essentially don‘t use WebRTC, but rather grab raw camera frames, H.264 encode them in software (using WASM!) and shove them down a Websocket (or WebRTC Data Connection. This lets them use their own encryption as well.
https://support.zoom.us/hc/en-us/articles/360048660871-End-t...