Actually it doesn't. It has more to do with what APIs the hardware is running. Does the target hardware support OpenGL ES 3.2? Does the target hardware support Vulkan? If not, what is the fallback?
Nvidia will probably announce an updated Tegra X1 that is faster and uses less power than PS4 or Xbox One at CES in a couple days. You take the "cell phone" comment as an insult or something. It is simply calling it what it is and where that hardware is commonly used.
And again, there isn't a 'full version' of UE4 and a stripped down mobile version.
