I was told by an old timer it was done to keep flexing down. The case hardening was done to make the metal less prone to flexing. The wood on most ejector guns gets very thin in areas and if the for iron flexes it tends to crack the wood easily. I took this with a grain of salt, being part Scott, I figure it was just ten cents cheaper to blue than it was to color. Lowest cost gun gets the lowest cost option.
One of the problems that Remington 3200's had was weak for iron metal. The metal on the fore end was so thin that it would flex and the stock would crack. They replaced thousands of fore ends due to cracks.
