Earlier quoted context omitted.
This is the typical great man myth that gets promulgated by their publicists to make them seem more than human. As a rule they are either out right lies or greatly exaggerated, other myths of this type is Kennedy reading 1000 words per minute, Napoleon listening to reports, reading a letter and dictating laws all at the same time, or Stalin single handedly designing the first five year plan.
1000 words per minute doesn't seem outlandish. My 10 year old already reads at over 300 wpm.
Your childs increase in reading speed by contrast is highly unimpressive.