> By this definition 100 humans pushing a stone have superhuman abilities.
Yes, that is accurate. A person with the strength of 100 people would be superhuman. A group of more-than-one humans has more-than-one-human abilities.
> This is not what superhuman means in an AI alignment context.
It is though, at least partially. Chess AI are great at chess because they play a shitload of it. Part of the power of AI is just being able to do the same things we do at vastly increased scale. Even if it could only do that, it would be dangerous.