The flaw is that graph is that it fails to specify the perf at iso-power comparison, or the power draw at iso-perf comparison.
The numbers they have both spoken and on their source website are very clear, but you evidently didn't even look at them.
If we compare our Efficient-core to a single Skylake core for a single logical process, we deliver 40% more performance at the same power.
If we compare our Efficient-core to a single Skylake core for a single logical process, we deliver the same performance while consuming less than 40% of the power.
Alternatively, a Skylake core would consume 2.5X more power to achieve the same performance as our Efficient-core.
If we compare four of our new Efficient-cores against two Skylake cores running four threads, we deliver 80% more performance while still consuming less power.
Alternatively, we deliver the same throughput while consuming 80% less power. This means that Skylake would need to consume 5 times the power for the same performance.
So again, these numbers that you claimed didn't even exist answer your supposed criticism.
If the comparison is done at an operating point which grossly favors one design, then it is extremely misleading, and you cannot extrapolate that comparison to other operating points.
Good thing they show a range of operating points in that graph. And elaborated more in text/verbally.