Sharing some information:
https://github.com/mendix/generator-mendix/blob/master/generators/app/templates/WidgetBoilerplate/src/WidgetName/widget/WidgetName.js.ejs#L76
Found a limitation on the https://apidocs.mendix.com/6/client/mx.ui.html#.action
Though documentation states that origin: this.mxform is not needed, it is not completely true. It is not working for full pages but does not work for popups. So this call action will close the page but not a popup. : (
So I think we need to reintroduce the origin again.
Cheers.