That's not remotely true. 1:1 shrinking doesn't occur as different parts of the chip have different densities and architectures are typically designed around a node so they wouldn't have been able to just shrink Fiji and realize all the perf/w benefits of a new node.
If we look purely at density and area calculations, 14nm Fiji would be around 300-350 mm^2. Improve clock speed by a conservative 30% and give it 8GB HMB2, and that should compete against the GTX 1080. What do you think Pascal is compared to Maxwell? Except a few minor tweaks, they're the same core.
AMD now has a 550 mm^2 Vega with 16GB HBM2 and at least the FE barely holds against the GTX 1080. So you can see where the expectations don't meet reality. It may be probably that they just over-engineered the thing. Sometimes simplicity manages to escape many engineers.