Ah, that might be due to a sub-state being active, rather than the root state.
After thinking about this more, I don’t think there is a concept of a “selected widget” in the sense of clicking on a widget to make it active. The vtkWidgetManager only provides information about the current widget selection underneath the mouse cursor. If you want the click-to-persist-selection functionality, I think you will have to listen for widget interaction.
let selectedWidget = null;
widget.onStartInteractionEvent(() => {
selectedWidget = widget;
// optionally change UI to reflect the selection
})