I didn't see him thinking that. Just that CPUs do not have as many bugs as other hardware - which I think is quite true. With CPUs a larger portion of bugs are found, and smaller bugs matter because they are not hidden by proprietary drivers.
FWIW, memory has plenty of bugs too. With respect to the original point, these are usually not visible to drivers (unless you count EDAC) because they're handled at the chipset level. However, for certain kinds of systems - especially embedded - that don't have chipsets these issues can become painfully visible. My own exposure to this was at SiCortex, where the memory logic was directly on the same single die as everything else that comprised a node.