Ah, now that I know its the NULL subsystem, I understand a little better.
Unfortunately the NULL interface is a very simple mocking interface when other platforms aren’t available. It uses a LAN beacon broadcast to listening servers which will respond when they get the request.
There is no filtering of the search criteria in this case, the servers just blindly respond. Code could be written to parse the request inside FOnlineSessionNull::OnValidQueryPacketReceived, but it was never written.
Typically LAN was more server browser-ish and on a much more limited scale of results so the server side filtering was left out of the implementation for time.
All major platforms (Steam/Live/PSN/etc) support server side filtering.