I think we place a greater emphasis on when Apple is actually the first to do something meaningful with an idea.
Yes, there was a tablet market before but it was pathetic and nearly dead before Apple got into it. If the tablet market pre-2010 (and pre-2007) actually matters at this point it does so in the context of history and perhaps some interesting trivia (in terms of who came up with what idea, that eventually got wasted by poor implementation.) Beyond that, be happy that Apple changed the tablet game and actually made it matter (an understatement, since Apple did much more than that, having put it at the forefront of computing moving forward.)
So in terms of actual viability (which is rather important), Apple was indeed the first in terms of multi-touch, tablets, smartphones, etc. Tech tends to mean so much more and reach its true potential under Apple. This phenomenon is a salient feature of the industry today, like it or not.