Yes, your not supposed to use thermal paste when using graphite thermal pad as that defeats the very purpose why thermal graphites where made for, which is a long lasting thermal pad solution that can be reused multiple times whithout the mess that you usually go through when removing thermal paste from your CPU.
Also graphite thermal pads are known to perform worse than cheaper thermal pastes like say the Arctic MX-4 or CM MasterGel Pro. Graphite thermal pads are best used when your testing out CPUs on multiple boards and want to save up on the cost that reaplying thermal compound like say a kryonaut usually has, and also in situations where you just want to set it and forget it without minding the increase in thermals, like say on OEM systems.
There are good Graphite thermal pads out there like the Thermal Grizzly - Carbonaut that performs just as good if not better than most thermal compounds available now, i just havent seen any of those being sold yet.