I've found noticeable uplifts in performance from tuning RAM timings on my 9900K, 3950X and 5950X systems.
I'll fish out some exact numbers later from the 5950X system. I'm not sure it's 25%, but it's quite a hefty bump, I'm sure it's over 10%.
A breakdown would be interesting to measure the effects of enabling huge pages, disabling next line prefetch,
and adjusting DRAM timing.