I think there’s an exception to this, at least as I read the official Microsoft VR FAQ. https://forums.flightsimulator.com/t/read-first-vr-faq/336918/2
There it states:
How do I preview VR Motion Smoothing in Flight Simulator?
Please follow the steps below to preview this improvement in the sim:
Install the OpenXR Developer Tools for Windows Mixed Reality from the Microsoft Store. You can get it here: OpenXR Tools for Windows Mixed Reality - Official app in the Microsoft Store 905
Launch the OpenXR Developer Tools.
Go to the Developer Settings tab and toggle the “Use latest preview OpenXR runtime.”
If you encounter any major problems, try turning the “Use latest preview OpenXR runtime” setting off and re-launching Microsoft Flight Simulator to see if the issue goes away. Please report any problems in the forums so that we improve the experience for everyone!
I don’t see any implication here that this VR Smoothing preview is limited only to WMR headsets.