MultiSelect not generating aria-controls attribute

[johnhoyland]

According to the docs, "The relation between the combobox and the popup is created with aria-controls attribute that refers to the id of the popup listbox."

As far as I can tell this is not happening. When I look at the HTML using the browser inspect tool, the generated hidden <input> element is not using the aria-controls attribute, and the generated <ul> element does not have an ID that could be referenced by such an attribute. I cannot find anything in the API that might enable this functionality. Have I missed something, or has this accessibility feature simply not been implemented yet?