Creator of Watercooler here.
I do agree with you that Electron is an amazing platform and definitely has a lot of cool, solid use cases, but that doesn't mean that every single app we use _should_ be written in Electron. Recently, it feels like every app uses Electron. Even the ones that shouldn't.
Video Conferencing is one of those apps that in my opinion should definitely be native for two important reasons:
1. Performance: Video conferencing needs great performance. As a user, you want the best video possible at the best FPS possible. Mostly Electron/JS video conferncing apps are not bad (Facebook Messenger, Google Meet) because Chrommium just provides a JS wrapper for native APIs implemented in C++. But, if you want to do anything outside of that you're screwed. You will eventually run into the limitation of what Chromium gives you and this gives you an upper limit to what you can do to optimize this.
2. Memory Usage: Video conferencing is usually used alongside other apps (while sharing your screen for example). For that reason, you want to minimize memory usage as much as possible to make it easier for the user to have the app open while using as many apps as they can. Electron uses a lot of memory.
A third reason is that the human interaction guidelines provided by Apple for their UIs (and embedded into their APIs) is very, very good. It keeps the user experience consistent across your platform and makes your app easier to understand. And this is coming from someone who is not really an Apple fanboy. What you see with Electron apps is a steeper learning curve for having to learn how to use every new app you install.