Is there a known bug with Maui Shell.FlyoutBackground?

Question

I'm playing around with styling the Maui Shell and have noticed some odd behaviour when Shell.FlyoutBehavior = "Locked".

The Shell.FlyoutBackground is not applied when the AppShell is fired up for the first time. It is applied if I change the main page to something else, and then assign a new instance of AppShell.

Can anyone think of why this occurs?

Initial state - It's grey when it should be blue.

After button click - Blue is applied

These are the relevant sections in my code:

public partial class App : Application
{
    public App()
    {
        InitializeComponent();
           
        App.Current.MainPage = new AppShell(); 
    }  
}

I have some styles which are supposed to be applied. They look terrible, but I wanted something which is easy to notice.

<Color x:Key="BlueTint">#550000ff</Color>
<SolidColorBrush x:Key="BlueTintBrush" Color="{StaticResource BlueTint}" />

 <Style TargetType="Shell" ApplyToDerivedTypes="True">
     <Setter Property="Shell.FlyoutBackgroundColor"
             Value="{AppThemeBinding Light={StaticResource BlueTintBrush}, Dark={StaticResource BlueTintBrush}}" />
     <Setter Property="Shell.FlyoutBackground"
             Value="{AppThemeBinding Light={StaticResource BlueTintBrush}, Dark={StaticResource BlueTintBrush}}" />
</Style>

And then the Shell xaml...

<Shell
    x:Class="Company.Product.OnMaui.AppShell"
    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
    xmlns:onMaui="clr-namespace:Company.Product.OnMaui"
    xmlns:res="clr-namespace:Company.Product.OnMaui.Resources"  
    Shell.FlyoutBackdrop="{StaticResource BlueTintBrush}"
    Shell.FlyoutBehavior="Locked">

    <!-- Shell Content items here -->
</Shell>

My Button handler...

[RelayCommand]
 private async Task StartShellExperience()
 {
     _shell = new AppShell();

     App.Current.MainPage = _shell;
 }

N.B. This window is translucent because it has Acrylic enabled, but I get the same result if it's off.