It means that the optimization on the 1.6.1 is worse than the 1.6.0, so if on the 1.6.0 your CPU runs at 50%, on the 1.6.1 it will run at 30% (the % are only indicative). It's more like the CPU on 1.6.1 is software-underclocked and Smash 4 need a certain CPU clock to run, because probably is CPU...