We aren't trying to measure each hardware set as apples-to-apples, but rather give the reader an idea of how performance characteristics for a chosen stack are affected by hosting environment. Specifically, we wanted the middle-of-the-road EC2 instances versus the extremely high-end Peak option to illustrate that difference.
I've noticed a weird trend where amazon created various slices of instance types a long time ago, and people have mentally gotten used to using larger ones far slower than moores law adds cores. So people will refer to something with 2 cores as "middle-of-the-road" and 32 as "extremely high-end" when in my brain thats "a cell phone" and "a 2 year old server".