When an item in a listview is selected from code behind, the selection will appear highlighted in the UI but the OnSelectionChanged event will not fire.
All other ListView controls that I have tested, including the Xamarin default ListView will fire the SelectionChanged event regardless of how it happens.
I would expect this to be the standard behavior since a listener for selectionChanged should not care about how the selection changed occurred.
(an ItemTapped would be expected to fire only in response to a user gesture)
The attached projects shows the difference in behavior between the SfListView and the Xamarin ListView when an item is selected from CodeBehind.