>There is no evidence or argument for exponential growth

I think the growth you are thinking of, self improving AI, needs the AI to be as smart as a human developer/researcher to get going and we haven't got there yet. But we quite likely will at some point.

and the article specifically mentions the fictional company (clearly designed to generalize the Google/OpenAI's of the world) are supposedly (according to the article) working on building that capability. First by augmenting human researchers, later by augmenting itself.