On paper or in a computer model, maybe. But I've had yet to experience this myself or meet a rider who didn't dislike sidewinds. Side winds catch clothing, the cyclist, spokes, you name it. This means they'll increase the amount of wind you need to push.

One other thing that is completely left out of wind calculations is the fact that neither wind speed nor direction is constant which will cause rider speed and cadence to vary even if you are a clicker. This is less efficient.