I worked at Zoom during this time. That's not what happened.

Zoom used the same technique Cisco Webex did - they ran a webserver with an open port so that local "links" to a meeting could open on your own machine. It wasn't a backdoor. Apple flagged that as a potential security risk, so Zoom worked with Apple on how to safely remove only the webserver without affecting other functionality. We were happy that Apple worked with us on this.

However, I thought it was very interesting (and strange) that there was almost no reaction from the tech community that Apple had software running on every Mac that allowed them to remove any binary they wished. (Which sure sounds like a backdoor)