Reaction time is the real difference in this video. A human can't react to the twitch of the siege tank cannon that happens just an instant before the shot land

Reaction time is the real difference in this video. A human can't react to the twitch of the siege tank cannon that happens just an instant before the shot lands, we treat it as something that happens instantly and thus, we can't react to it, not even with a single unit. If you apply a human reaction time to that AI, that behavior isn't possible anymore, even with perfect micro.