According to the seller, the rear access doors added to the rear wagon door was related to this wagon being an ice-cream vehicle.
https://www.facebook.com/marketplace/item/1164321511268804
“1951 Willy’s Wagon. All original four cylinder engine! Granny 4 Speed, withnivertide. 4-wheel drive very rare. 3-way ice cream truck with style rear doors. New wiring harness. Runs good. Great surf wagon project with good bones. Firm 7500,”