>>12716785A made up graph can have meaning by being a simple representation of your thoughts. He could have written a text instead saying : there is a possibility that machine intelligence will surpass human intelligence and grow exponentially fast.
What is wrong with asking " hey guys, what if we continue on our current path and then this happens?" Tell me.
Intelligence is a widely used concept by everybody, and widely used by everybody to compare humans or animals in terms of how intelligent they are. It's often imprecise for the reason you outline, but that doesn't mean the concept of intelligence is useless. You can also come up with different ways of quantifying intelligence to male it more precise.
Maybe the "power" part of the axis name is superfluous, but that doesn't make the whole graph meaningless, you can remove it in your head if you want. Being pedantic about these things is not very productive.