Benchmarking and its methods are a total mystery even to moderators, apparently.......
You benchmark at lower resolutions to push the CPU to the limit to test its actual capability. Same reason you test a GPU at 4k even if it cannot push 4k properly. A CPU test at 4k is as pointless as a GPU test at 720p. This gets explained every time there is a CPU benchmark and people still cant comprehend it.
Also, high refresh rate gamers? You know, the guys who do esports and competitive shooters? They all play at 1080p, and they want HIGH framerates. So its not a useless test anyway.
Dont forget games like Factorio, that slurp up those cache gains, or games like starcraft II and sins of a solar empire/rebellion.