- Editing Multiple Issues at the same time
The dropdown is not expanding correctly as well.
This information appears to be added in JIRA 6.4 Release Notes where the feature is introduced but not yet included in the documentation itself:
Another notable improvement has been how JIRA handles bulk editing of multi-select fields, like Version and Components. Now, you're able to select whether you want to clear or add to all the existing values, replace all the existing values with a specific value or set of values, or simply remove a specific value or set of values.
Include this information in the documentation.