The problem is basically a variant of Goodhart's law: "When a measure becomes a target, it ceases to be a good measure."
Publications want to use these benchmarks as a convenient proxy for real-world performance. Phones have "benchmark detection" and run their power management with different settings when they detect that a benchmark is running, defeating the purpose of running the benchmark.
BTW, I don't think this is about gaming vs. non-gaming workloads (there are different benchmarks for those), or even running plugged-in vs. on battery. My understanding is that some of these "benchmark modes" are so aggressive that the phones would become too hot to hold in your hands. No sane phone manufacturer could use settings like these for real-world usage.