When a custom field of type User Picker is created to use the User Picker & Group Searcher Search Template the issue type context with which it is asosciated is not respected when filtering on issue types. The user picker custom field remains in the Search Panel even though issue types not associated with it are selected.

Note. If the user picker custom field uses the User Picker Searcher Template though it does respect the issue type context with which it was configured. So the custom field appears and disappears according to its issue type context.