As the Station Sedan link mentions, Packard sold some station wagons ("brakes" as they are sometimes called in Europe) pre- World War 2, but this body style was difficult to make on the Clipper design. However, when the Clipper body was facelifted for 1948, a station wagon inspired special body design was added. A normal station wagon body is in the form of a large, rectangular box that includes side windows and a large access door or doors at the rear of a car. The Packard body did not lend itself to a boxy rear, so a relatively narrow, yet high, extension was grafted onto the sedan body. Wood was used for part of this added structure -- standard station wagon construction practice before the 1949 Plymouth all-metal wagon appeared. Wood decorative panels were added to the side doors to provide even more of a station wagon look.
So the Station Sedan name was actually a pretty accurate description: It was a sedan with a narrow, roof-high extension that could hold more things than the sedan trunk could, but was less useful in that regard than a true station wagon would have been. Plus there was the unavoidable "woodie" problem of maintaining the wooden parts with new coats of varnish annually and other detailing.
The result was a vehicle with many impracticalities that never sold very well. Worse, it was based on the bloated 1948 Packard design that failed to attract many buyers once the postwar sellers' market ended at the end of the 1940s.
This is a photo I took at the Ft. Lauderdale Antique Car Museum in 2013.
This rear view shows how narrow the "wagon" feature was. The car had a double rear door, the part containing the rear window swing upwards and the lower part dropped down in conventional tailgate fashion.
I include this photo so that you can see a regular Packard sedan and how its rear design served as the basis for the Station Sedan model.