They probably don't have a 6700K or Kabylake system to test with. That's the impression I've gotten.
IIRC they benchmarked and reviewed a 6700K when it came out, but then it never showed up in any later testing. Probably got sent a review sample that they had to send back.
Ok, so let's assume for a second it's a question of lack of availability (which I question because there's a lot of i7's already in that list including the AFAIK bloody expensive 5960X, and 3970X which is Sandy Bridge-E), then they OC the most recent overclockable 4-core i7 they have to emulate a recent i7 going the speed of a stock part they're missing with a note on the review to say that's what they've done and why.
Furthermore, for someone to have that many processors available for testing, they can't just be going on review samples. This isn't someone who is 'going pro' in the review field on a budget, this is someone who very obviously has gone pro some time ago. I'd also question the idea that a reviewer would still have a 6700 on loan: It's launch date was Q3 2015. If they had recently asked for one to be loaned from Intel, surely the latter would respond saying they would prefer to loan a more appropriate part such as the 6700K or 7700K. What self-respecting reviewer would buy a 6700 instead of a 6700K? Even if they got the 6700 *and* 6600 for free, surely a regular CPU reviewer would question the point in having everything they need to review a 6700K and not bothering to shell out for the processor, when they're comparing it to other flagship parts. Coming back to the idea that they're going pro on a budget, surely one would sell the i3-2100, all the low-end FX CPUs, the Sandy Bridge i5, the SBE i7, and probably have enough to pay for a Devil's Canyon, Skylake or Kaby Lake i7, K type CPU?
- edit - I've just read frozentundra's post after yours, but it's too much like hard work at this time of morning to re-write my response accordingly
