Inspiron G5 5000, DDR4 memory speed

Hey folks. The spec sheet for the G5 desktop says max memory speed is 2666MHz, but when I open Alienware command center and CPU-Z it's being reported as 2926MHz (or 1462x2). It's the original memory that it came with and is being reported as 3200 speed (I realize that it won't run that fast).

I recently updated the BIOS to 1.0.5 but there's no changelog to tell me if that was responsible or not. I do not know what the memory was running at before I updated.

Can someone shed some light on this for me? I want to order a set of 16GB but am now confused as I didn't think there was a point in ordering more than 2666MHz.

Thanks!