According to this article:
www.formula1.com/news/article/130.html Williams is working hard in their aerodynamics, and will have new bodywork for Sepang and a new undertray for Interlagos. Can somebody explain what the difference is between launching a new car at the beginning of the season and then modifying it radically during the season, and starting the season with a heavily modified "last year's" car and then introducing a new one in the middle of the season (like Ferrari and McLaren). Is it not the same thing? And if not, why not?