Memory matters
And just as the LGA2011 chips enjoy a greater number of cores and threads, the quad-channel memory controller's bandwidth is needed to feed the CPUs' appetites.
The benchmark isn't perhaps fully taking the IVB-E architecture into account; the write bandwidth absolutely should be higher than the 3960X's.
Memory latency becomes more important as the number of threads increase. There's no tangible increase over last-gen 3960X.