I have heard this argument before, if it’s identical workloads you get faster output but the same total work. Thus “faster performance” seems correct for fixed workloads and “more performance” is correct on games or benchmarks where you get more FPS.
I still think “faster performance” sounds sound odd, but I understand their point.
"M1 Ultra has a 64-core GPU, delivering faster performance than the highest-end PC GPU available, while using 200 fewer watts of power."
Note that they say "faster performance" not "more performance". What does "faster" mean? Who knows!