RootFolder property doesn't work for modernize ForderBrowserDialog

• .NET Core Version: .Net Core 5.0 from master branch: 5.0.100-preview.5.20262.7

• Have you experienced this same bug with .NET Framework?: No

Minimal repro:

1. Create a Winforms .Net Core Application
2. Add following code to show modernize folderBrowserDialog and set its RootFolder property to specific Folder

       public Form1()
       {
           InitializeComponent();
           FolderBrowserDialog folderBrowserDialog = new FolderBrowserDialog();
           **folderBrowserDialog.RootFolder = Environment.SpecialFolder.CommonStartMenu;**
           folderBrowserDialog.ShowDialog();
       }
   

3. Build and run application

Actual behavior: RootFolder property setting doesn't work, please see following screenshot:

Expected behavior: RootFolder should be changed in modernize folderBrowserDialog, see below screenshot in old folderBrowserDialog(.Net Framework behavior)