Well, Gary, you've halfway answered your own question. If Audio Path says it's outputting 2 channels, it's outputting 2 channels. If all the DSP studio modules are turned off, including output format, then it cannot upmix. So if your description of MC is correct it cannot be doing what you say it's doing.
So either your description is wrong, or your conclusion is wrong. All we have to go on is your say so that MC is outputting 5.1. Please provide some proof of that in the form of a screenshot or photo of your receiver diagnostic screen.
You have not provided any meaningful explanation or description of what MC is connected to, or how you are playing back, or how your system is configured. (PC outputting sound to what device? TOSLINK? HDMI? Receiver? DLNA? How is the other device configured?) If you have your PC hooked up to a receiver, are you aware your receiver could be applying a sound field? Your sound card driver could be applying a sound field.
We have nothing to go on, except you talk about using WASAPI and testing with Windows Media Player (things only available on Windows) and using Windows10, and yet you're posting in the Mac forum. What should we make of that? Are you running emulation of some kind, or did you just make a mistake?
So it would be helpful if you could provide some additional clarity about how you are hooked up, and what exactly you are doing. Because the evidence you have provided so far either contradicts your claim, or indicates some component other than MC is involved.