Furthermore, your apparent wind is so far forward than sheeting in is actually the correct trim for the main.
by the same logic, why do we "blow" the rotation downwind? It seems excessive to allow 90 degree rotation when the apparent wind is still ahead. I don't go to 90 deg, but you get my point.
What an echo in here! ;-)
What they said.
We rotate to 90 because although the apparent wind does move forward, it rarely comes much more forward than 70 degrees. It's still much more to the side than when you sail upwind.
In light air, you will find it necessary to induce a bit of twist in the main - particularly so the bit of sail above the spinnaker can still breath as it is mostly unaffected by the redirection of air over the main. In moderate to heavy air, being sheeted hard IS proper trim and the additional mast rotation helps induce some extra fullness in the mainsail for a little more power.
