It's always tricky extrapolating from focal cognitive effects to overall performance. For example, small amounts of cannabis or alcohol can also greatly attenua

It's always tricky extrapolating from focal cognitive effects to overall performance. For example, small amounts of cannabis or alcohol can also greatly attenuate the obsessive internal rumination (a.k.a., "the jitters") that can sabotage many kinds of performance. Of course, it's dose-dependent, because eventually the detrimental effects on attention and memory (as you correctly point out) will outweigh the beneficial anxiolytic effects.