Yes this is correct.
But as you see the original un-optimized version was running at nearly same speed on both. Meaning the A15 and Core i3 performance are comparable, if run at the same clock.
The general perception has been that the raw performance of the ARM CPUs(like A15 and A57) and Intel Sandybridge CPUs like the one inside like i3/i5 are not in the same ball-park . Most people believes they are leagues apart. Also one of the reasons why such comparisons havent been made before, much.The idea of the blog is to show that this is not completely true.
Not meant to counter your argument, but at least one compiler out there (GCC) is - in my experience - very good at finding optimizations for x86 but fails most of the time for ARM unless you provide very clear and very strict hints in your code. NEON optimization is one of them. It wouldn't be the first time that GCC completely ignores intrinsics in my loops or (I kid you not) introduces 16-bit Thumb code in my 32 bit code. Very frustrating to constantly have to second-guess your compiler.