Why Ms called Windows on ARM "Windows RT" and not "Windows Metro" ?
I know they pondered calling the Windows version that's to run on ARM based devices "Windows Metro" and the only reason I believe they did not go with that name is to adhere to the nature of the new kernels architecture. Since in actuality the "Metro" runtime/libraries can be found on both Windows for x86 and Windows for ARM, so calling it Windows Metro they thought is not right since all the new SKU's have the metro runtime.
But still I am of the strong opinion that they should have called the ARM edition of windows "Windows Metro", the consumer does not know any better and they would understand the Windows 8/Pro also have the Metro UI and apps just by looking at it, since all the version look identical visually.
But calling the ARM edition "Windows Metro" would also sort of signify that this can only run Metro apps and is intended to be primarily used in Metro mode, not desktop.
Some other suggestions I saw which I like include:
Windows 8 Lite - This is good I reckon.
Windows AIR (ARM in RealTime)