I have noticed that some events are not created by zwift. There is probably a way to make them public, the club I belong to does it by invitation only. It's a bit awkward. OTOH, it would be weird if a batch of people we don't know showed up*. But since the riders we know are from all over the world, some people might show up that know us.

*I was going to call them randos, but we're a batch of randonneurs. So we're the randos.