I don't think anybody is really saying it is. Academics treat big-Oh performance on very very full hash tables like a sport. Real world code on real world CPUs

I don't think anybody is really saying it is. Academics treat big-Oh performance on very very full hash tables like a sport. Real world code on real world CPUs often has a more complex cost function than what the academics considered; cache sizes, fitting in a cacheline, memory bandwidth, icache pressure, ...