Scary.. I was just looking at that 5 minutes ago LOL. Roller spring is PN 5845 which is single with damper, about a 485 lb/in rate per the numbers. Flat tappets are PN 5767H, single with dampers, about a 325 lb/in rate.
So nothing obviously different besides probably the spring wire and lesser coils length so hard to spot unless you know them by heart.
Those Hughes springs that the OP lists above are a heavier rate than the Edelbrock flat tappet springs..... those Hughes springs are 385-400 lb/in.