The problem with Haswell K-chips (especially retails) is that IMC capable of running PSC at 1333+ 8-12-8-28 on air even at Pentium core/cache speeds is ridicilously difficult to find.
Another problem with result reliability are the frequency-dependant voltage holes with PSC at 1333 and onwards. For example, you can have a kit capable of doing certain settings at 1.78-1.79 all day long, 1.80-1.84 will fail first loop for no apparent reason, 1.85+ will work fine again. When you're on air binning mems, you're usually not in a hurry so you can figure such things out. But when you're pushing other components and just want stable RAM clocks, this might indeed be a big nuisance.
In general, I think that PSC (and may be also some BBSE) are the only ICs running which at high speeds (1333+) with high-clocked i7 is noticeably harder than with low-clocked Pentium. So yes, low-clocked results might be misleading in a way but if you take that into account, you can still make a decent judgement on kit quality rather than shelling out hundreds of dollars/euros on forums/ebay for kits without a single listed result.
What comes to the other ICs - from what I've experienced so far on different kinds of Samsung and Hynix, you get a bigger voltage difference going from board to board than from going from Pentium to a 5GHz i7.