“Don’t know why. Todays metallurgy is more advanced. Modern CNC offset grinding could reproduce virtually anything.”
Well, anything can be done if you have enough money. And if the original crank was forged, that might be a heck of a lot of money, CNC or not.
But doing a crank for an ME 109, you're not going to find a casting. It more than likely WILL be a forged billet. Probably in the $3k-$4k range.