Rémi Bernon (@rbernon) commented about include/windows.ui.viewmanagement.idl:
[default] interface Windows.UI.ViewManagement.IUISettingsAnimationsEnabledChangedEventArgs;- }
 - [contract(Windows.Foundation.UniversalApiContract, 8.0)]
 - [marshaling_behavior(agile)]
 - runtimeclass UISettingsAutoHideScrollBarsChangedEventArgs
 - {
 [default] interface Windows.UI.ViewManagement.IUISettingsAutoHideScrollBarsChangedEventArgs;- }
 - [contract(Windows.Foundation.UniversalApiContract, 10.0)]
 - [marshaling_behavior(agile)]
 - runtimeclass UISettingsMessageDurationChangedEventArgs
 - {
 [default] interface Windows.UI.ViewManagement.IUISettingsMessageDurationChangedEventArgs;- }
 
These aren't needed now.