For that kind of scam, all you really need the cooler, which are often parted out for legit reasons (watercooling, replacements, probably some specialized high-density and rackmount plays) and may be available as a spare or "second-shift" offering.

It would probably be easy to produce a PCB that's the right size to fit a 4090 cooler, but just contains 90 cents worth of random SMD parts. And you can produce them in quantity when you want them rather than relying on an erratic supply of stripped "real" PCBs.