Since the actual mechanism in the Choose dialog does not support multiple selection, the UI should reflect this by removing checkboxes (which imply multiple selection), and only hilight a row upon click.
Eventually we must improve choose dialogs to support multiple selection - see related ticket MGNLUI-3197

Use case, Illustration of problem:
I try to add an item to a set of items using a default Magnolia control.

Please see screenshot.

1. Click "Add"
2. Choose 2 items
3. Save

--> only one item is chosen - this is completely misleading. I was so happy to be able to choose multiple items ;