The author writes about success. His statement is: with more work you can achieve the same success than another person with a higher IQ.
==> Work irons out ones inferior IQ.
Actually mastering a field or craft, or having success simply requires a lot of work.
Working harder can reduce some differences, but no one without an adequate level of intelligence is going to be a competent, much less really successful, mathematician or physicist or any intellectually challenging field.
What do you consider as an adequate level of intelligence? And what kind of intelligence? I suppose that being a manager requires a lot of social intelligence...
The problem I see: to balance out a deficit, one has to work more or to delegate that work.
The advantage I see: everyone is different, so that everyone contributes different things in his field. Yes, the basic level of understanding needs to be, but everything else is open.
Actually mastering a field or craft, or having success simply requires a lot of work.