Background color on mobile app above and below the ContentPage is white instead of black

I have a VS2019 for mac cross platform Xamarin Forms 4 app. I used the basic template to create it.

In my App.xaml.cs file I just set the MainPage to my ContentPage object.

This content page has the backgroundcolor set to black.

When I run it on my iPhone I get the following results. Notice how the top of the screen and the bottom both have white backgrounds. I can't seem to figure out where that is coming from.

I tried wrapping my content page in a NavigationPage and settings its background to black, but all that does it add a little more black at the top of my contentpage and move the rest of the page down.

I can't figure out where the background color for the top and bottom outside of my content page is being set.

Can someone tell me?

UPDATE: Added some things asked for in the comments:

App.xaml:

<?xml version="1.0" encoding="utf-8"?>
<Application xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:d="http://xamarin.com/schemas/2014/forms/design" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="UpdateAgent.App">
    <Application.Resources>
    </Application.Resources>
</Application>

App.xaml.cs:

using System;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace UpdateAgent
{
    public partial class App : Application
    {
        Interfaces.IStartup Startup;
        public App()
        {
            InitializeComponent();

            Xamarin.Forms.DependencyService.Get<Interfaces.IStartup>().Init();

            MainPage = new WebUpdatePage();
        }
    }
}

Visual Studio 2019 for Mac is latest version. Just updated the other day and when I check for updates there are not any.

I am using an iPhone XS Max not the simulator.

After seeing the comment I tried it out in the simulator the iPhone 12 Pro Max - 14.2 just to see if it was any different. It does the same thing.

UPDATE 2: Decided to add the WebUpdatePage xaml and class figuring it would be asked for eventually. Here they are:

WebUpdatePage.xaml:

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         xmlns:local="clr-namespace:HybridWebViewMobile;assembly=HybridWebViewMobile"
         x:Class="UpdateAgent.WebUpdatePage"
         BackgroundColor="Black">
    <ContentPage.Content>
        <local:HybridWebView x:Name="hybridWebView" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" />
    </ContentPage.Content>
</ContentPage>

WebUpdatePage.xaml.cs:

using Xamarin.Forms;
using Devices.Communication.Mobile;

namespace UpdateAgent
{
    public partial class WebUpdatePage : ContentPage
    {
        public WebUpdatePage()
        {
            InitializeComponent();

            DependencyService.Get<IConnectDevice>().RegisterDetectors(hybridWebView).Wait();
            DependencyService.Get<IConnectDevice>().Jsonfunctions(hybridWebView);
        }
    }
}

UPDATE 3:

Here is information about the HybridWebView:

The first iOS class is this:

[assembly: ExportRenderer(typeof(HybridWebView),typeof(HybridWebViewRenderer))]
namespace UpdateAgent.iOS
{
    public class HybridWebViewRenderer : HybridWebViewRendererMobile
    {
        public HybridWebViewRenderer()
        {
        }
    }
}

The second iOS implementation partially looks like this (only show the relevant parts):

public class HybridWebViewRendererMobile : WkWebViewRenderer, IWKScriptMessageHandler
{
    const string JavaScriptFunction = "function invokeCSharpAction(data){window.webkit.messageHandlers.invokeAction.postMessage(data);}";
    WKUserContentController userController;

    public HybridWebViewRendererMobile() : this(new WKWebViewConfiguration())
    {
    }

    public HybridWebViewRendererMobile(WKWebViewConfiguration config) : base(config)
    {
        userController = config.UserContentController;
        var script = new WKUserScript(new NSString(JavaScriptFunction), WKUserScriptInjectionTime.AtDocumentEnd, false);
        userController.AddUserScript(script);
        userController.AddScriptMessageHandler(this, "invokeAction");
    }