RDGClientTransport?

Question

There are a number of forum threads throughout the Internet discussing the work around of adding the registry below, to get RDP working. I'm asking for official public documentation of why and when this is necessary, or an alternate solution and the location of that public documentation. This seems to affect some Windows 10 installs but not others. I had an .RDP file that was working for me but not a client. Neither of us had this registry but once I added it to the customer's registry the .RDP file worked.

HKCU\Software\Microsoft\Terminal Server Client\RDGClientTransport DWORD 0x00000001