Почему SelectedItem у ListView срабатывает только 1 раз, а SelectedIndex — всегда?

<ListView ItemsSource="{Binding Items}" 
		  SelectedItem="{Binding SelectedItem}"
		  SelectedIndex="{Binding SelectedIndex}"/>

public MyTestModel SelectedItem
{
	get => selected;
	set
	{
		selected = value;
		Debug.WriteLine("SelectedItem");
		RaisePropertyChanged();
	}
}

public int SelectedIndex
{
	get => index;
	set
	{
		index = value;
		Debug.WriteLine("SelectedIndex");
		RaisePropertyChanged();
	}
}

SelectedItem
SelectedIndex
SelectedIndex
SelectedIndex