Much obliged Waftrudnir,
Let me give you another perspective. It is easier to work on hides or skins during the summer. The skins are nice and thin. But that is all they are? Summer coats! During the summer big game shed their previous coats and grow new ones. Come fall and freeze up, they have brand new coats set to endure for the winter. This is the hide you work with. It only makes logical sense not to grab your summer jacket when you go outdoors at forty below...or ten below for that matter. For the moose, the skin is thick and becomes uneven. So that is why it has to be frozen to cut for the right height of thickness during the shaving process.
Commercial hides on the other hand are dyed with chemicals. It is a false claim of the tanning process. They are not truly dry when the compounds are in them.