This should not harm benchmarks unless they mark their threads as background. As for a particular strategy I presume Apple could, for example, use 6 high-perfo

This should not harm benchmarks unless they mark their threads as background. As for a particular strategy I presume Apple could, for example, use 6 high-performance cores instead of 4+4 hybrid. But then thermal management will be an issue. So the choice was about throughout/latency/energy efficiency. Using simple low-performance cores for tasks that can wait is very good strategy as one can put more of those cores as opposite to running the performance core under a low frequency.