WinPE 10.0 - Open and Listening Port appears filtered/closed externally

For a variety of reasons, we are trying to open up a port in WinPE. The intent is that a security application would be able to detect winpe images on the network by communicating over that port.

We have a powershell script that runs in Winpe. and connects system.net.sockets.TCPListener to the port in question, lets say 1899.

On the Winpe host system, netstat -ab returns:

TCP 0.0.0.0:1899   <hostname>:0 LISTENING

However, externally this port cant be scanned by nmap or by nessus, and appears closed for all intents and purposes.

In a full windows OS (win7, or win10) if we bind system.net.sockets.TCPListener to port 1899 with the same code, teh port appears open and accessible.

Any ideas?