If the bootloader, all of the services, the kernel, the window manager, etc were open source, but edge was closed source and bundled in a separate version of Windows then yes I would consider Windows an open source operating system.
Because the desktop OS is used for so much more. But if the core functionality is missing, the point is lost. A better analogy, as you like to play games, is a VPN company releasing their app as open source, after being critiqued for privacy issues. Only to find out just the GUI was released but the rest can be installed using a plugin system.
The analogy is lost here because the core is open source but the GUI is not. Core system services do most of the heavy lifting for these apps and that remains in AOSP.
