Question on TOP

[wacki]

on page 126 sklansky says 2 pair is a 9-1 underdog against a pat flush on 5 card draw. How is this possible?

With 4 outs, I would think 2 pair would have would win 4 out of 47 draws to get the full house. Thats 4 (out) to 43 (non helping cards) or 1 to 11. Basically a 11 to 1 underdog. Am I right and sklansky wrong?