Erm...hold on a second, there. You can watch television while playing games (or: one person watching television with the other one gaming). Games that don't require both screens.
Precisely, it was one of the main points they brought up in 2011, how past systems 'hog' the tv and wii u changes that, however it was way before TVii was announced. most likely in production though
In addition to that, that TVii is some sort of advanced television guide/VCR/video on demand service. From what I've seen, these are mostly touchscreen controlled (with the television screen not doing too much until you actually select something to play). And that automatically makes it pretty hard to play games at that same time.
Yea the UI is centered around the pad, but look at the 3ds: it allowed you to 'pause' at any time via the home menu- only you were limited to the system apps from there. maybe TVii is one of WiiU's system app, or better yet Wii U can handle more than 1 app that demands more than just a system app a la 3DS
However, once you've got something set up to be played...I think it'll be possible. Using netflix to stream something to your television while at the same time using your controller for a one-screen game. I haven't seen it confirmed...but it is about the only reason I can think of why the OS may need that amount of memory.
My thoughts exactly