Does GP Widget handle validation from Python Toolbox published as GP Service?

[tigerwoulds]

I have created a python toolbox in ArcGIS Pro that I want to share as a GP Service. The user inputs their Portal URL, username, password and the GIS Server parameter dynamically provides a dropdown with a list of GIS Servers federated to the Portal. Based on which sever is selected, the GIS Folder provides a dropdown list with available folders on that server.

This works great in ArcGIS Pro. But when published to ArcGIS Enterprise as a Web Tool/GP Service, my Geoprocessing Widget in WAB does not provide the dropdowns. In fact, nothing happens. Is there a way to keep my validation code working in the GP Widget?