Hence brute force, the Ai wins because it can do stuff at a faster rate than humans (microing) - it has more computing power, and can do many things at once at different locations.
Not really a fair competition when humans are involved

Of course ANY AI would win if it micros units "intelligent" at 100% cpu power with a 6 core 3ghz cpu. This is the inherent problem with making real time AI's that can play "fair" against humans. And why most of them are "limited" via some kind of max APM and max "attention hotspots"
Obviously AI vs AI is another matter (so in this content it isn't cheating per sé, but humans playing against this AI have no chance to win once the dynamic strategy responses are of a broad enough scope.)