XMP \ OC

Dear Knakso,

The memory controller is integrated in the CPU, and it is not on the board.
The memory controller , runs optimal at 3200MHz, with DDR4, and 4800MHz when using the D5 version of this boaprd (DDR5).
https://ark.intel.com/content/www/us/en/ark/products/134589/intel-core-i512600k-processor-20m-cache-up-to-4-90-ghz.html

That your system wil have better performance when you ocverclock the CPU, that is a myth, basically when you go beyond the speed of the integrated memory controller, only a synthetic memory benchmark program, will show better values, but it doesn't result in higher, overall system performance, unless you run it at lower latency timings.
XMP is a set of values, that is supposed to work with all the thousands of combinations of CPU, chipset, and AMD, or Intel motherboards, it is not guaranteed to work.
Gskil is a memory assembler, not a memory manufacturer.
https://www.crucial.com/support/articles-faq-memory/truth-about-memory-manufacturers
it could very well be, that your 2 kits have different chips, or are produced in a different batch.
I have seen kits that were purchased in ine buy, one had 512MB Hynix chips, the other kit had 1GB chips of another brand, but the partnumber on the box was the same.
Personally I have always, good results with Patriot Viper kits.
And maybe th ememory controller in your CPU, can simply not handle higher speeds