Yes - A site admin (screen pictured above) can disable it, but that is site-wide for all hosts that schedule events. There isn't a way that an individual host can do it. Personally, I like to have it on, it confirms to me that people are registering and I can see real-time results, but after a while it is a lot, so I create a rule in Outlook (right click on message) and have them automatically go into a folder rather than my inbox.
I found a way to do this just the other day when I was going through options on the Webex Administration page. I personally haven't enabled it but it should do the trick for you!
