I remember a few years back someone made a program to set your own JEDEC values and flash them into the RAM stick, pretty cool.
There should be at least CL8 at 1.5 in JEDEC, but CL7 is pushing it. Most MB’s bios use the relaxed CL9 to boot with a higher success for the first time. Not everyone realizes that so they don’t run their RAM at full potential. Most average MB’s don’t even have the XMP feature to draw on the faster values and users are too afraid to mess with memory timings.
Most RAM chips begin their life as CL9 but are “binned” to find the faster ones where they get sorted to whether they make it to CL8 or CL7. Others are just simply a higher-end manufacturing process that gets better yields of the CL7 or even CL6.