Geekbench is a series of extremely short and bursty benchmarks. Because of this, it doesn't really test the steady state speed a system is capable of, it's more

Geekbench is a series of extremely short and bursty benchmarks. Because of this, it doesn't really test the steady state speed a system is capable of, it's more testing the peak performance for short periods. In this view, it's entirely possible that the Air simply did not have time to throttle before the benchmark ran out.