Well, yeah. The term "internet tablet" as you are describing was what Nokia used to describe their line of cell-phone-sized pocket computers. However, that term has not caught on outside the world of Nokia. With the rise of the iPad (and all the Apple marketing that goes with it), the term "tablet" is now firmly associated with a device that is much larger than a cell phone and lacks a keyboard. (If you add a keyboard, it becomes a "netbook" or something.)

A device that fits in your pocket is now firmly defined as a "cell phone". (As much as I hate to admit it, nobody anywhere seems to make pocket computers any more. And "smart phones" are getting dumber by the day...)