Imagine, you have event type for group of 2 people.
There are 3 ways of how you can set it up in Who panel.
When any required host is available.
In this case external person of your event type after selecting a time can pick host manually among those who are available for that time.
2. When all required hosts are available. In this case you would have to manually pick a default organizer yourself.
If you have Notify & Accept in How do you handle proposals panel, chosen one becomes organizer.
If you have Notify & Hold in How do you handle proposals panel, host who accepts proposal becomes an organizer.
3. When specific (requested) hosts are available. External person starts by selecting hosts they want to meet with. Meeting proposal is sent to all selected hosts. The host who accepts the proposal becomes the organizer.