Microsoft and Qualcomm's biggest issue is actually not about the fps numbers or benchmarks, it's about reliability. Many steam games would simply not run. It's not about making them gaming machines, it's that they expose reliability issues or holes in the OS/Hardware ecosystem.
If there is a chance that a certain program would not run, it damages trust. Gaining trust in the ARM ecosystem is paramount. I'm afraid prism and x86/x64 emulation hasn't fully addressed.
Preferably, all software should run seamlessly. Then we can talk about benchmark or fps numbers.