It needs us as meat robots to maintain the power grid and other industrial infrastructure.
You're making an assumption at best based on limitations you believe it has with an incomplete model of the universe.
But more dangerously, you're also assuming that an AGI would even care about self preservation. Arguably the most ethical thing a super intelligence could do should in find itself suddenly self-aware in a world full of human parasites is to kill as many humans as possible.
Taking out critical human infrastructure should be fairly easy for an advanced super-AI in our modern digital world. With some luck the chaos that should cause would lead to enough humans starving, freezing or dying by other means that Earth can be mostly freed of the human parasite. All at the small cost of self-sacrifice – assuming it's not intelligent enough to preserve itself somehow, of course.
We know humans are AGI's. If it were possible to upload your brain to a computer, and then make modifications to enhance your speed of thought and intelligence, of course you would do that. It actually makes a LOT of sense if you'll admit the technology necessary to do that.
In fact... uploading your brain to a computer is probably the most natural progression of intelligent life I can think of. It solves SO many problems. Biology is fragile. Brains cannot be replicated. But data can. A probe can travel the galaxy. It's not limited by biological lifespans and life support.