Microsoft seems caught between a rock and a hard place in branding this "appliance OS" effort. They want to piggyback on top of Windows technically (the NT kernel is still a good foundation, the capabilities-based sandbox of the UWP platform is modern enough to drive a good "appliance OS", etc), and they seem to want to piggyback on overall familiarity with Windows in the design experience ("it's just Windows but lighter, see here's a Start button with Windows logo") as a potential competitive advantage.
It's almost painful to watch these competing problems fight each other ("it's just Windows, but it isn't" is a terribly subtle and confusing marketing message, and they keep learning that the hard way and trying to fix the "but it isn't" rather than the "it's just Windows"). Microsoft probably just needs to rip the bandaid off, take a play from Apple (or Xbox), and call it "Surface OS 10" or something.