Well, I wouldn't consider XMP as a real overclock but just as a maximum clock (frequency) manufacturer considers as full speed for that particular RAM stick model. That is not a traditional overclock that meant going over manufacturer's recommended frequencies. Some RAM has several such XMP profiles that are just set of instructions for BIOS to set memory to certain frequency including other settings like Cas and voltage for instance for it to work at all or at it's best performance. JEDEC is also similar but may include even more detailed settings.
Conversely, if CPU can run from a set minimum frequency to it's maximum frequency on all cores is also just a set of steps in frequency and not real overclock but just normal operation within given (projected) parameters set by manufacturer to their least successful sample. That's why moist can be "overclocked" to more than that.
The manufacturer of the RAM ICs says it's DDR4-2666. It doesn't matter who pushes it to a higher level, it's still a higher-than-rated clock. The RAM is indeed DDR4-2666 regardless of how the company that puts it on a DIMM advertises it.
Let me put it this way: Remember when OCZ sold bone-stock Samsung PC-800 RDRAM as PC-1066? And remember that it overheated on most systems? And remember what we said about it back then? You might not have been around back then, but the consensus was "overclocked too far".
Regarding that old memory, Samsung manufactured it. OCZ overclocked it.
Moving up to the present, the memory referenced in this article was originally Samsung DDR4-2666, sold by Adata as DDR4-3200. Samsung manufactured it. Adata overclocked it.
From another angle: If the chips on these modules weren't being overclocked, XMP wouldn't be necessary.
As for CPUs, do you remember when Intel tried to release a Pentium III 1.13GHz using the Coppermine core? And remember the math error? Uncovering that put Tom's Hardware back on the map. Intel had used a raised vCore to get that CPU to that frequency, and the consensus in the enthusiast community was "overclocked too far". But since Intel was the actual IC manufacturer, you could instead say "improperly validated", and that's closer to the argument you're making.