I've seen this in the documentation and I'm seeing this behavior and its leading to significant clutter in my organization's content:
"When you create an event, a group is automatically added to your ArcGIS Online enterprise organization. It's important that you do not delete this group because it shows you who is attending your event."
We are using hub for an initiative that will have 100+ events - and we were intending to use Hub for 30+ similar initiatives every year. In 3 years we will have 10,000 groups...that's simply not going to work.
This seems very unnecessary simply to track who is coming to an event. Couldn't this be stored in data file in the Initiative's group?