NO.So almost exactly 50% higher Geekbench scores than A8
If we assume DDR4-3200 is used, the 6s has twice the bandwidth of the A8 in iPhone 6. That alone would yield (2^2)^(1/10)=14.9% higher Geekbench scores (memory synthetics are weighted with 20% geometrically).
That means the remaining benchmarks improve by 1.5/1.149=30.5%. The would require a A8 clocked at 1.4GHz * (1.305^10)^(1/8) = 1.95GHz.
Since it is only clocked at 1.8GHz, we can infer an IPC improvement of 1.95GHz/1.8GHz = 8.5% (assuming limited sensitivity to raw bandwidth)
That's pretty close to what was predicted here.
Cheers
Your distaste for GeekBench lead you astray, you are not looking at the actual data, as it turns out the memory bandwidth subtests yield lower improvements than the integer and floating point ones.
STREAM does not generally yield maximum theoretical bandwidth results. There is a reason why the test has several different components. Download the source, flip some compiler switches, watch the results fluctuate. As they should depending on architecture and compiler.