Set View Definition Should Update Popups Across All Maps/Apps (not just in item details).
Currently, when you add a field to an hosted feature's item details, the new field is not automatically configured in Views created from that layer, so you must Set Field Definition to correct for this... the problem is: the popup in WebMaps/Apps that the view is already in do not automatically reflect the new view definition.
This means that to see the new field in all view popups in your maps and apps, you need to configure popup in each map that this layer exists in.
Note: the new field shows up in attribute table, just not in popup.
Support info: Setting a Hosted Feature Layer View Definition
Problem: this does not update across WebMaps that contain the view.