I know..... I don't really trust MS to tell me what day it is. And we're supposed to take everything they say as if it was from God himself.
But let me clarify my post a little further. No matter what I'm doing on a PC, or in Windows, I always try to take the most direct and fastest route to get to my objective.
After doing much reading, and rejecting complicated methods, I finally determined that just renaming that CortanaCore.dll file to CortanaCore.ddd would totally disable it. Because that .dll file is the thing that makes it work. Cortana could be re-enabled later, by just renaming it back to the original .dll.
I was doing that manually, on every Windows install till I fingered out how to put the steps into a simple batch file. Now I run that batch file as a part of my Windows Install with every Install.
I know it's Old Hat, but I at least attempt to do everything via the K.I.S.S. method.