Why doesn't CollectionView highlight SelectedItems within RefreshView - xamarin

Question

I'm getting two collections of data from a web service - the full collection and then a subset of items. The subset should be selected on load. I cannot get the SelectedItems to show as selected in the CollectionView, event though that property is set. I've looked over the Monkeys example and all over the web but can't find an example just like this
View:
<RefreshView IsRefreshing="{Binding IsBusy, Mode=TwoWay}" Command="{Binding LoadItemsCommand}">
<CollectionView x:Name="ExperiencesCollectionView"
ItemsSource="{Binding Experiences}"
SelectedItems="{Binding ProfileExperiences, Mode=TwoWay}"
SelectionMode="Multiple">
<CollectionView.ItemTemplate>
<DataTemplate>
<Label
Text="{Binding Description}"/>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
</RefreshView>
</StackLayout>
Code Behind:
public partial class ExperiencesPage : ContentPage
{
ExperiencesViewModel viewModel;
public ExperiencesPage()
{
InitializeComponent();
BindingContext = viewModel = new ExperiencesViewModel();
}
protected override void OnAppearing()
{
base.OnAppearing();
if (viewModel.Experiences.Count == 0)
viewModel.IsBusy = true;
}
ViewModel:
public class ExperiencesViewModel : BaseViewModel
{
public ObservableCollection<Experience> Experiences { get; set; }
public ObservableCollection<object> ProfileExperiences { get; set; }
public Command LoadItemsCommand { get; set; }
public string InterestedIn { get; set; }
public ExperiencesViewModel()
{
Title = "My Experiences";
Experiences = new ObservableCollection<Experience>();
LoadItemsCommand = new Command(async () => await ExecuteLoadItemsCommand());
}
async Task ExecuteLoadItemsCommand()
{
IsBusy = true;
try
{
Experiences.Clear();
//Get these from the REST service
var experiences = await App.ExperienceManager.GetExperiencesAsync();
var serviceExperiences = await App.ExperienceManager.GetProfileExperiencesAsync();
foreach (var exp in experiences)
{
Experiences.Add(exp);
}
foreach (var profileExp in serviceExperiences)
{
ProfileExperiences.Add(profileExp);
}
}
catch (Exception ex)
{
Debug.WriteLine(ex);
}
finally
{
IsBusy = false;
}
}