The odd thing is, Memory overclocks are still very motherboard dependant. Most of the reviewers that have issues with getting memory to 3000Mhz or higher are using Asus or MSI boards.
The Asrock Taichi, and Gigabyte Aorus boards don't have similar issues. Joker had his RAM at 3000Mhz on day one with his Aorus.
Level1Tech had high speeds with the Taichi as well.
On some boards you need to increase BCLK, but one other you don't.
We also cannot ignore that XMP memory has been tested and verified for Intel systems, and memory controllers. We've only seen G.Skill so far bring out AMD compatible RAM. Then again it seems most of their kits have had the least amount of issues once again also.
Level1Techs managed to get their 1800X at 4.2Ghz with 3200Mhz RAM ( 14-14-14-34 Timings) with their Taichi. This was March 8th for the video as well, and there have been other motherboard updates since then as well.
http://valid.x86.fr/u5xhc7
https://youtu.be/VjGWqTFultI?t=15m24s