Well, that seems barmy. Different players would inevitably have the ball in their stance in diffreent places and therefore the shaft lean would be wildly different from player to player.
Mizuno might suggest that a players should have 8 forward lean on a shaft while
Ping think a player should have 10^.
What would be needed would be a way to compare them, which requires a snigle starting point. The only single starting point would be the shaft to be vertical. Besides anything else, it doesn't matter at all what the loft IS, only that it is measured in a consistent way from club to club?