Manufactures typically set the the iron number based on launch conditions and not loft of the club. They talk about it a little in the rocketbladz THP radio episode. If you look at specs between the AP2's, MP-59's, MB and MC the loft is different from set to set from manufacturer to manufacturer because they are looking four optimal launch angle, ball speed,ect.ect.ect.
No no no. This horse is dead and needs not to get beaten.