I watched all of the event live and I feel that that graph is deceptive. If a game is 15 minutes and has 3 main battles lasting 15 seconds each, and you use 100 average APM on non-battle time and 1000 APM during battles, your average APM will be 145 but you obviously have a superhuman advantage.
This is compounded by the fact that almost all of AlphaStar’s actions are “useful” whereas a significant amount of the human actions are spammy.
You will typically see a human select a group of units, and fast-click a location in the general direction they want the units to move (to get them started moving that way), and then keep clicking to continuously update the destination to a more precise location. Every click counts as an action. An AI can be perfectly precise and “clicks” the right place the first time.