TL;DR the author attempts to measure the ratio between native and emulated performance using Microsoft Prism on Windows. His measurements suggest that the emulated performance is very close to native performance.

Though I am not skeptical of the authors methodology, I do suspect that the ARM64 build of WoW may not be as "optimized" as the x64 build. This is because in some of his workloads the emulated game actually outperformed the native game.