Disable Attendee Unmute is a feature that, when used in conjunction with Event Mode, will give you a more traditional, organizer-driven call. Like Event Mode, Disable Attendee Unmute is only available to the call organizer and their delegates.
When turned on, attendees on the call who are muted aren't able to unmute themselves until the feature has been turned off again.
Turning this on can be very helpful on a big all company call where you want to make sure there aren't any interruptions. If there's a Q&A session, you can turn the feature off, allowing attendees to unmute themselves, ask their question, and re-mute themselves once their question has been answered.