I have verified it on several other original cars as well so I know it's consistant, I can only assume that it's a feature added for 340 cars as they might be driven more agressively than a 318 car. Such a small thing but Chrysler wasn't known for adding cost for no reason, there must have been some failures in testing so the engineers addressed it.

*BTW, the "C" washer is roughly 1/16" - 3/32" thick.