Separate inner doors for each shelf/compartment were a feature of several early freezers. It was a feature that provided extra insulation and eliminated loss of cold air when retrieving items. It was a matter of simple organization to categorize and label each compartment so that you knew where to go for what. In those days, there were few transparent wrappings or packagings for frozen food so you had to read, not just glance, in most cases anyway. I remember Kraft paper and coated papers, the famous "drugstore wrap" and freezer tape for protecting frozen meats.
One of the things that contributed to the high operating costs of side-by-side refrigerator-freezers was that when the freezer door was opened a 5 foot column of zero degree air fell out to be replaced by room temperature air that had be be cooled back to zero F.