I don't know who said that, but he may have been talking about sail trim. I have studied the subject and now have more doubts than I started with. C.A. Marchaj wrote a definitive book about sailing theory and relates boom angle to wind speed. Of course the most important thing is the angle of the sail to the wind and that also depends on things like leech tension. Nevertheless, for what it is worth I made a graph that I consider a starting point for positioning the boom on the Omega 14.
Bear in mind that boats differ and I know that some classes center the boom whenever they can.