Unless there are in-depth APM limitations on the AI, there's no contest for AI vs. A human.
AIs have a long way to go to beat good human starcraft players.
Just from a pure economy standpoint, any computer process has quite an advantage from just optimizing action queues and keeping idle workers working.
People have already created TAS programs that can take out infinite numbers of enemies with minimal stock (ex: medvac/tank vs. infinite ultralisks). Or have zerglings that perfect 1 siege blast per 1 zergling splitting.
As far as micro, AI already has proven capability to absolutely dominate human micro, like not even close.
As far as build paths and macro decisions, AI isn't there yet but all it takes is one player and one programmer to come up with an in-the-middle and well-rounded build path that doesn't lose to any cheese; Sacrifice some economy to just have an army at all times_ and the AI will micro dominate the rest in extremely, humanly impossible army trades (I mean winning a 40 stock vs. 200 stock army battle).
Honestly just imagine having ONE mutalisk perfectly micro all-game, never receive death damage that just outputs as much damage as humanly possible at every angle. And you could have all 20-140 of your army stock doing this at all points in the game.
No contest. Just hasn't had time devoted to it yet.
It turns out that being really good at narrow micromanagement situations doesn't add up to winning complete games. StarCraft is messy and difficult.
And EVEN THOUGH they have access to ridiculous APM and the ability to do BS cheese strategies like that, they STILL suck.
Seriously, go watch some of these games. The AIs are freaking terrible, despite the fact that they basically cheat at the game.
Also, the AIs "perfect" micro, frankly only applies at the individual unit level. IE, they can kite like no tomorrow with a singular marine, but as soon as you have anything more complicated than that, such as "fight with 10 marines", well you learn that the AIs can't so much as form a concave.
Yeah, those 10 marines are all INDIVIDUALLY stutter stepping, but it turns out that perfect stutter stepping doesn't matter much when your army is cut in half, due it being split up.
Controlling more than a couple units "perfectly" (with regards to each others actions) seems to be out of reach of any AI out there.