Yes it is. Because Sandberg never says she admires her brother because of that fact. She says she admires her brother, and then states that fact about the brother. Greenspun is the one who makes the false connection. Here is the full quote:

I should have understood that this kind of self-doubt was more common from females from growing up with my brother. David is two years younger than I am and one of the people in the world whom I respect and love the most. At home, he splits child care duties with his wife fifty-fifty; at work, he's a pediatric neurosurgeon whose days are filled with heart wrenching life-and-death decisions…

With Greenspun's logic, you could equivalently claim Sandberg admires her brother because he is a neurosurgeon.