DDK label_hover_text not working

Dash Python
1

The usage guide says:

ddk.ControlItem also takes a label_hover_text parameter, which will add tooltip-like hover text to your label.

However, this feature does not appear to be working, neither in the example in the documentation nor in my code. It doesn’t produce an error, just no hover over the info icon. I’ve tried in both Safari and Chrome browsers.