The process of lapping makes the heatsink base smooth to a near mirror finish, which improves heat conductivity.
Over the last few days I have installed the CPU and heatsink into the motherboard to get it ready for installation.
Look at the three golden heat pipe, that was the best thing I ever saw for a CPU heatsink.
I was dubious of whether I needed a shim but after fitting this heatsink I concluded that it is not needed.
But the impression left by the arctic silver after a test fit convinced me that the heatsink and core are mating adequately well.