Those tools are for generating images and art, not precise schematics. The post is criticizing them for failing at something they aren't meant to do.
Who says that? Where does it say that Dall-E and Stable Diffusion are only for generating images and art? Why are graphs not images? And why can't they be art?
Those are models that generate images from textual prompts. Aren't you just moving the goalposts by saying they can't generate specific kinds of images?
The homepage defines the process: "starts with a pattern of random dots and gradually alters that pattern towards an image when it recognizes specific aspects of that image"
So based on that description and context clues, I wouldn't expect it to generate a precise schematic.