The end of the article explains this all quite well: Programming is very easy to get into professionally. I know we all like to think of ourselves as super smart and that our knowledge is somehow hard to come by, but in reality, it can be as easy as picking up a book. You just can't do that in most fields, even "easy" ones.
As a result, you get a wide variance of commitment, and therefore talent.
It is also perceived to be easy to get into, walk into a bookstore and see all the "whatever for dummies" books. So there is a huge army of low-grade "programmers", many of whom are now unemployed. That is true across the entire planet, mind. So while there is a shortage of true talent, that won't be solved by importing the "... for dummies" crowd from overseas.
As a result, you get a wide variance of commitment, and therefore talent.