A thread where people express a different opinion is NOT hijacked. Yes it is disappointing and tear some after so much testing to also have to explain things you might consider self explanatory, but that's not thread hijacking. Just different opinions. Different perspectives.
What I see from that Hard|OCP testing.
2600K is 4 cores, 8 threads. 2500K is 4 cores/4 threads. In those tests the i7 920, a much older processor, when overclocked at 3.6GHz was also faster than the 2500K. Again the i7 920 a 4 cores 8 threads processor. So the extra threads helped in low resolution testing and in games from that period.
Fast forward to 2015 and something seems to have changed.
https://www.techspot.com/article/1039-ten-years-intel-cpu-compared/page5.html
Based on your testings, the 2700K, a faster version compared to the 2600K, against 2500K scores almost the same. So that 20% faster you are saying, based on the low res testing from Hard|OCP in 2011, 4 years latter ends up being a fantasy. Never happened, or just gone because of the advancements made in programming.
Also while you don't have an i7 920 in that testing, you do have a i7 870, that it is faster than a stock 920?(Intel. WT...?) Well, that advantage the 920 was enjoying in the low resolution testing that Hard|OCP did, is also gone. In 2015, the 870 is slower than the more modern 2500K, when in 2011 and at ultra low resolutions the 920, or any other processor close to that specs, was looking much much more future proof than a 4cores/4 threads 2500K.
YOU CAN NOT make conclusions based on low res testing in PRESENT games. It looks logical, but things change. Minimum requirements change, the way games are programmed is changed, what hardware companies try to push in the market changes. Based on TODAY, the 8400 is a miracle. But this miracle will fade much faster than what your low resolution testing makes us believe.
Please Don't see this as a hijacking. Just as a different opinion.