ComboBoxのSelectedItemを参照するReactiveProperty<Visibility>が反映されない

前提・実現したいこと

WPFでMVVM（素のWPF+ReactiveProperty）に挑戦しています。
ComboBoxのSelectedItemの値に応じてVisibilityを変動させたいと思い、以下のようなコードを組みました。

Model.cs

csharp
1    public class Fruits : BindableBase
2    {
3        public ReactiveCollection<Fruit> FruitsList
4            => new ReactiveCollection<Fruit>()
5                {
6                    new Fruit() { Name = "Apple", Price = 100 },
7                    new Fruit() { Name = "Orange", Price = 130 },
8                    new Fruit() { Name = "Peach", Price = 200 },
9                };
10        
11        private Fruit selectedFruit;
12        public Fruit SelectedFruit {
13            get { return selectedFruit; }
14            set { this.SetProperty(ref selectedFruit, value); }
15        }
16
17        public class Fruit
18        {
19            public string Name { get; set; }
20            public int Price { get; set; }
21            
22            // Bind時の表示項目
23            public override string ToString(){
24                return this.Name;
25            }
26        }
27    }

MainWindowViewModel.cs

csharp
1public class MainWindowViewModel : BindableBase
2{
3    public ReadOnlyReactiveCollection<Fruits.Fruit> FruitsList { get; }
4    public ReactiveProperty<Fruits.Fruit> SelectedFruit { get; }
5
6    public ReactiveProperty<Visibility> AppleSelected { get; set; }
7
8    public MainWindowViewModel()
9    {
10        var fruits = new Fruits();
11		
12		FruitsList = fruits.FruitsList.ToReadOnlyReactiveCollection();
13
14		SelectedFruit = fruits.ToReactivePropertyAsSynchronized(x => x.SelectedFruit);
15		
16		AppleSelected = SelectedFruit.Select(x => x.Name == "Apple" ? Visibility.Visible : Visibility.Collapsed)
17			.ToReactiveProperty(Visibility.Collapsed);
18	}
19}

MainWindow.xaml

xaml
1<StackPanel Margin="5">
2    <TextBlock Text="好きなフルーツは？"/>
3    <ComboBox ItemsSource="{Binding FruitsList}"
4			  SelectedItem="{Binding SelectedFruit.Value, Mode=TwoWay}"/>
5	<TextBlock x:Name="Select" Text="{Binding SelectedFruit.Value}"/>
6	<TextBlock x:Name="ShowWhenSelectApple" Text="Apple選択時のみ表示したい" Visibility="{Binding AppleSelected.Value}"/>
7</StackPanel>