Of course their frames are differently sized. The point is the geometry, the relationship of the saddle to the pedals and handlebars. Normally, shorter people have less drop from saddle to bars; the reverse is true of Sastre and Nys.
I don't mean to pick on anyone, but there's this common misconception ("myth") that smaller frames handle better than correctly sized frames. The opposite is true, because when the frame gets smaller, saddle height stays the same. So the handlebars move down and away from the rider, even though top tube shortens. In Sastre's case, this is a deliberate decision to get a more aggressive, aerodynamic fit, but if he raced cross you would probably see a more classic setup like Nys'.