The "Type" field of "Event" contains unpublished terms, for users with 'Administer terms' permission. It creates some issues when the "Event" is created with the unpublished term of "Event type", users without 'Administer terms' permission couldn't see it, and it didn't make sense.
Create two terms of "Event type" taxonomy:
Go to the event creation page /node/add/event - you will see both of the terms in the "Type" selector.
Change a reference method of the "Type" field from "Default" to "View". Create an "Entity reference" view of "Event type" taxonomy terms with filter - "Published: true". Set this view as a reference method of the "Type" field.
Closed: won't fix
13.0
Code (back-end)
This issue is not relevant anymore, as Taxonomy has permission administer vocabularies and terms that allow users to see unpublished terms create new vocabulary, etc.