Shared custom folder on Mac host is 'Read Only' in Windows 10 guest

I'm using a Windows 10 guest on a Mac host to develop and compile for Windows. To avoid code duplication I try to share my code repository on the Mac host with the Windows guest using Custom Folders in the Sharing/Share Mac settings. The permissions are set to 'Read & Write' in the Parallels settings' dialog for the code repository folder. The folder is shared and accessible in the Windows guest. The only problem is that all folders inside the code repository folder is 'Read Only' in Windows, so I cannot open any Visual Studio projects in there. These folders are not 'Read Only' in the Mac host.

Why are all subfolders of a shared custom folder marked as 'Read & Write' in Parallels settings 'Read Only' in the Windows guest when they are not 'Read Only' in the Mac host?