Understandable but currently it is listed in the interface as a "Override" which implies that the Joomla name is used unless the override is specified. It is also not showing as a required field but I think you are aware of that.
Aye going also to change the label (without override).
Is there any reason why there is a place to set up organizers but when creating events, the organizer list has all Joomla users on it rather than just the Organizers I have configured?
The reason is that Matukio does not know which of your users are organizers - on some installations organizers maybe normal editors, on others administrators and on some in multiple own created user groups. I first thought on a setting (Which Joomla user group does contain your organizers for example), but this would limit organizers to a single group (i know users can have multiple groups but you would always need to assign your organizers into it) and so i left it as it is.