虽然这个问题不会出现在所有的windows 11机器上，我不知道为什么，这里是解决方案：
通过将以下行添加到MauiProgram.cs中，可以调用函数
setBorderAndTitleBar（false，false）;
问题已解决。（只有#If Windows和#endif之间的行。

/// Need to use the 2 following name spaces:
#if WINDOWS 
using Microsoft.UI;
using Microsoft.UI.Windowing;
#endif

namespace MauiAppWindowTest
{
    public static class MauiProgram
    {
        public static bool NoTitleBar=false;
        public static MauiApp CreateMauiApp()
        {
            var builder = MauiApp.CreateBuilder();
            builder
                .UseMauiApp<App>()
                .ConfigureFonts(fonts =>
                {
                    fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                    fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
                });
/// The Code below was added
#if WINDOWS
           builder.ConfigureLifecycleEvents(events =>
           {
               events.AddWindows(wndLifeCycleBuilder =>
               { 
                   wndLifeCycleBuilder.OnWindowCreated(window =>
                   {  
                          IntPtr nativeWindowHandle = WinRT.Interop.WindowNative.GetWindowHandle(window);
                          WindowId win32WindowsId = Win32Interop.GetWindowIdFromWindow(nativeWindowHandle);
                          AppWindow appWindow = AppWindow.GetFromWindowId(win32WindowsId);
                          if (appWindow.Presenter is OverlappedPresenter p)
                          {
                              /// Calling this function resolves the issue
                              p.SetBorderAndTitleBar(false, false);
                          }
                   });
               });
           });
#endif
/// Up to Here

            return builder.Build();
        }
    }
}