My understanding is that Scanavo just manufactures the steelbooks and ships them to the distributor (film company).
They will then insert the discs, add the J-cards and other relevant items and shrinkwrap the package.
Spine slashes under the shrinkwrap don't seem to be quite as common as through the shrinkwrap (where the slashing took place at the retailer), but hey, it's still human beings who open the packages at the distributor, and they can make silly mistakes like everybody else.
But this is such a simple problem to solve! Amazing that this hasn't been fixed years ago. Bu no, they just keep on destroying the merchandise around the world