Hum. When I try to use WDRT, it misidentifies my phone as a Win JR LTE. (It's actually a Win HD LTE X150Q.) That's suspicious, so I don't allow the automatic process to go forward.
If I manually select the correct hardware model, and follow the on-screen instructions to kick my phone into manual upgrade mode, WDRT never recognizes its presence, and the restore doesn't proceed. So I cannot use WDRT to revert back to 8.1.
On the other hand, initially using the Upgrade Advisor to go from 8.1 to 10586.X went smoothly, and regular OTA updates have successfully brought me through all the normal production builds of Windows 10 up to 14393.67; I'm stalled there now.