His logic, which reverses the calculations that DaringFireball blogger John Gruber used to predict the screen dimensions of the iPad Mini almost four months before it was officially announced.
There is an argument that has been made (see post in DaringFireball for the math) that the scaled-down iPad could run existing iPad apps, just with smaller touch targets.
Fireball (or are we intimate enough for me to call him Daring?) points out further that Apple has never had even a majority of the smartphone market: let alone of the total mobile phone market.