From the comments section in the link you provided:
"Did anyone actually go back and read what Arthur Clarke wrote about these things?
They’re “Newspads” — and the paradigm is very different from either a ‘tablet’ or a TV per se: on the other hand, let’s just say I hope Jeff Bezos isn’t planning a similar defense strategy for the Kindle
The thing is a reading device, intended for what would constitute requested push content (say, an ‘edition’ of s ‘newspaper’). The keys let you navigate between pages, and perhaps (touch sensitivity not allowing gestures) moving a virtual larger newpaper page so you can read different sections at high default magnification. Moving images were subsidiary to the newspaper metaphor: illustrations with some TV-like character. There is a scene in the movie (during the Pan Am trip to orbit at the beginning, ISTR) where we see a NewsPad working as a newspaper (in black-and-whitish display) with moving illustrations
Running the thing as a portable flatscreen television is a different thing (and, assuming bandwidth exists, would be a logical “gee whiz!” thing that a forward-looking person in the ’60s might imagine his newspaper would turn into someday. But keep in mind — it would be far more ‘interactive’ than a typical TV metaphor, as you could select any number of running video windows within the ‘book’ or ‘paper’ you were reading. Not single-window push like broadcast TV at that time"