The A12X is a 10 billion transistor 7 nm 12W chip.
The i6700K is a 3 billion transistor 14 nm 95W chip.
If you assume linear scaling on all three metrics (bad assumption, but rough rule of thumb) you get 10/3 * 14/7 * 12/95 -> 85%, roughly in line with benchmark results.
The i7 6700K is also a SoC and includes a GPU (weaker than the A12X's) and many other components that are also included in the A12X. It doesn't have quite the same level of integration as the A12X, but characterizing one as a 'SoC' and the other as a 'CPU' is inaccurate.
Power to performance is far from linear (and gets worse the higher you go). High TDP desktop chips are pushed to the point where a marginal increase in performance would require a massive increase in heat.
The i6700K is a 3 billion transistor 14 nm 95W chip.
If you assume linear scaling on all three metrics (bad assumption, but rough rule of thumb) you get 10/3 * 14/7 * 12/95 -> 85%, roughly in line with benchmark results.