How does the AI "know" which Zergling is going to be fired upon? Are the tank shots not instant-hit? Or is this just a demonstration of what actual optimal control would look like.
The tanks aren't given overriding manual commands, so it likely could just predict how their automatic targeting works. If a player would give commands, it could get at least some information from the animation frames before the target is aquired and the shot fired.
(The implementation in the video likely just cheats and gets the information from the engine, but at least the first case should be deterministic enough)
There's almost certainly a bunch of timing-based micro with animations/game ticks/etc that a machine would find. For example, if a machine does a sequence of actions with sub-millisecond precision they can pop a unit into range, fire, and then pop back out again without being fired upon over and over.
A lot of units would be rendered useless because it's balanced for humans. That means the units they counter would be a lot stronger. I'm afraid it would probably just be a race to get the fastest rush.
What you're describing is called "kiting", and is already being done by regular players (not to mention the pros). It is only possible for some combinations of units, for example Marines with stimpack vs regular zerglings ("slowlings"), or Viking vs Void Ray because one unit needs to be fast enough to be able to shoot + move out of range before being shot.
They do say that they will limit the number of actions taken by the AI to focus on building a smart and strategic AI instead of learning gimmicky micro moves, but if one thing is sure, it's that even the best micro cannot win a StarCraft game if the macro is not on point, and bad choices are made (good luck micro-ing siege tanks against a swarm host!)
Rushing is a bit of a rock paper scissors situation. You can beat a fast rush by doing a slightly slower rush that focuses more on economy, and winning via defenders advantage.
I haven't played SC in a few years, but I think I can give a basic answer.
There's would not be one optimal strategy, but many optimal strategies depending on the matchup between units. By taking advantages in differences in movement speed, attack range, attack projectile speed, and attack cooldown, a weaker group of units can potentially beat a stronger group.
This is an older video that demonstrates some examples of winning with good micro: https://youtu.be/CdSKD3LRHV8?t=11. An AI knowledgeable of and capable of executing such tactics would be pretty strong.
Just on the surface, these sorts of games are notoriously difficult to balance properly. Someone discovers a strategy that tips the balance, and units/abilities/whatever have to get nerfed. The odds that there's a stable balance at a level of play not actively tested (e.g., infinite APM) are extremely low.
One example is a sibling post's video of 100 zerglings against 20 siege tanks. For humans, the zerglings are capable of destroying only a handful of tanks before being killed of. For an AI with infinite APM, they can move all but an individual targeted zergling out of the way of the tank's splash damage. This allows them to take out all of the siege tanks with only moderate losses. Many such matchups will be tossed on their heads, and it's likely that one of them is totally game-breaking.
There is a lua widget in spring rts that allows for units with at least one farsighted unit to automatically stay out of los. Sneaky army will wriggle through all defense lines.
Void rays are countered by AOE anti air. With infinite APM there is no need for two rays to be hit by the same aoe. Further AOE tends to do less direct dammage, so VR with infante APM may hard counter a lot more unit types than intended. IMO, the risk is more from something like blink stalkers becoming insanely resource efficient.
Simple example would be in combat, like being always out of range ect ...
Imagine one army where every single unit is controlled by one human. Each individual unit would be very very strong.
Infinite micro? I'd just send all drones/probes/SCVs directly to the human's base and kill their drones. The extra drones that the human has wouldn't be able to make up the difference.
This is already an infamous strategy (worker rush) and it os easily countered as long as you have all your workers united and attack at once (not much micro can be done at that point, and the numerical advantage trumps that... unless you're playing protoss and constantly trying to replenish shields, and still!).
Also, I'm pretty sure this is not something that DeepMind would do to "solve intelligence".
still a tough question but they could do some insane things. for instance if they had 200 marines and controlled each individually i can't imagine what they'd do. for humans it's requires insane mechanics to even break them up into 8 seperatel groups and control them for more than a few seconds
If you could issue as many orders as you wanted, what would the optimal strategy be?