If you're talking about the general concept of using js to spoof another protocol: that exploit involves middleboxes sniffing TCP connections at the packet level, rather than at connection/stream level. It certainly won't work for connections with a TCP server.
If you're talking about using that exploit to allow access to the victim's machine from the internet: that won't work because listening interface for the x11 server is localhost, not the LAN interface.
If you're talking about using that exploit to allow access to the victim's machine from the internet: that won't work because listening interface for the x11 server is localhost, not the LAN interface.