I am thinking there is a core charge for liners if buying genuine cat, and from what I gather, you are buying refurbished pistons and liners when buying genuine cat, they have had some trouble with them, their rebuilt heads too.
Don't feel bad, my lawyer who I've know for 45 years still looks at my like that when I try to explain things, I told him he had to take a class how to look clueless.
Know for a fact there is a core on liners from genuine Detroit kits sent many back they dont want them re used again.
They don’t rebuild liners, pistons, rings, wrist pins or bearings, they are not reusable. Heads, blocks, rods, turbos, water pumps, are rebuildable , that’s why the core. This rule was only for buying rebuilt or remanufactured parts. Buying new did not require a core. You were buying new, not rebuilt. They wanted the core to rebuild and resell, if you bought a rebuilt part.