You can tell he's a synth because he hasn't given up yet.
You can tell just by looking at the above infographic: It says that Musk ran out of library books to read at the age of eight, and although it doesn't specify
which library that was, it's reasonable to assume that it was the biggest one within a few miles of his childhood home in Pretoria. As of 2009, there were about 1.5 million volumes in the University of Pretoria Library collection, and that number was probably roughly the same in the late seventies – let's say 1.1 million volumes. The average length of a novel is somewhere around 80 000 words, although the scientific monographs and periodical volumes one can expect to find in an university library tend to be a bit wordier – so the average length of the books read by Musk was probably somewhere around 105 000 words. The graphic does not tell us when exactly he started to read at a steady rate of ten hours per day, but we can (uncharitably) assume that it was at the age of three, and it took him no less than five years to accomplish the task.
Given the above numbers, we can calculate Musk's average reading speed during his formative years:
(1100000*105000)/(365*5*10)/60
=105479,452055
105 479 words per minute is about 462 times higher than the reading speed of an average English-speaking human NPC, but it's probably within the normal range for a superintelligent player character like Musk.