Memory overclocking can have a huge effect on application performance -- depending on the app in question. One of the key features of Intel's new Arrow Lake processors is that they can support stratospheric memory transfer rates. However, that may only apply to the high-powered "K" series processors, at least if ASRock has any idea what it's talking about.
As spotted by Uniko's Hardware, the memory QVL for ASRock's Z890 Taichi high-end Arrow Lake motherboard shows verified memory speeds as high as 9066 MT/s on the Core Ultra 200 K Series Processors. However, uniquely, there's a drop-down on the page to switch to the "Core Ultra 200 non-K Series Processors." Doing so reveals that the highest verified memory speed is a still-speedy 7200 MT/s.
To be clear, DDR5 memory running at 7200 MT/s is still overclocking, and a significant step up compared to the official spec of 6400 MT/s for the nascent Arrow Lake "K" series processors. We don't know what the official memory spec of the "non-K" Arrow Lake parts will be, but we'd wager it will probably be 5600 MT/s. Why? Because those parts will have lower power limits, and hot-clocked DDR5 actually draws quite a lot of power.
That could be the same reason that the "non-K" series parts apparently can't overclock as high, too; it's entirely possible that the extra power consumption required by super-high memory clocks starts to have a detrimental effect on power-limited Arrow Lake CPUs. It's also possible that this data could be based on early sample processors that simply don't overclock as well as the K-series parts.
However, the most likely explanation is simply that ASRock hasn't tested the non-K processors on the 2.xx BIOS yet. When looking at the QVL for the Core Ultra 200K-series CPUs, we see that the highest memory speeds were achieved using the 2.02 BIOS version, while there are no results for that version on the "non-K" QVL. It could simply be the case that ASRock is focused on testing the parts that are about to hit retail on October 24th.
Intel traditionally does limit memory overclocking on lower-end motherboards, but this is to our knowledge the first time that there has been (or may be) a difference of this kind between -K and non-K processors. Frankly, given that DDR5 memory capable of hitting more than 7200 MT/s is still significantly more expensive than DDR5-6400, we doubt this difference will matter to most users.