Reading this mailing list thread, I'm really not a fan of 'Linux' application that only work on WSL2. This feels wrong and some would qualify it as the expand part in EEE (embrace, expand, extinguish).
But ... but that's not what the email says, at least from a casual reading.
> We would like to build it such that in theory any Wayland compositor could add support for this mode of operation if they want to remote application to a Windows host (over the network, or on the same box).
I'm not really in the state of mind to fully parse the full email chain, but it sounds like they want the ability to extend Wayland to forward a wayland window/application over RDP to an RDP client. This isn't really WSL2 specific, and could be used to forward applications from a dedicated Linux machine to a Windows client, or maybe even to another Linux host running FreeRDP!
I know the idea of using RDP at all isn't very sexy on Linux, but FreeRDP is nice, and you don't need to use windows at all to benefit from it. IMO it's pretty nice for when you need a detached session, especially per user sessions or multi sessions per user. Definitely better than VNC, again IMO.