GE used plastisol dishwasher interiors, because
It’s greatly reduced cost to manufacture, and most of all because it greatly reduced expensive damage claims because of porcelain chipping.
Porcelain chip complaints nearly put KitchenAid out of business, we used to scrap so many brand new dishwashers because they had chips tanks. And the problem got really bad when they KD 18 series dishwashers were released because they took the gasket off the edge of the door and customers would drop a dish on the edge of the door and made a nasty chip and there was no way you could get out of having to replace the entire door in warranty.
This is why whirlpool and Frigidaire cleverly went to a molded plastic inner door because of the durability of it.
GE was always a low level dishwasher until the 80s when they actually got serious about building dishwashers and one that actually cleaned and was fairly durable.
John.