I agree that the author is making a point about art being an acquired concept. I am not entirely sure what an achievement concept is, but it seems to be a specialized term. I suspect it has to do with the set and normative notions people have about what counts as achievement or success. Depending on one's social and intellectual affinities, for example, getting representation from a certain kind of gallery counts as a proud achievement, while showing with a gallery that does not fit one's socially defined achievement concept will be experienced as missing the mark. And one's social media might be full of photographs that succinctly demonstrate nearly identical achievement concepts to those found on the feeds of other artists of one's social milieu. Similarly, collectors, gallerists, and others in the art world will have acquired such concepts