I think the introduction of the word taboo clarifies the discussion. Vance obviously doesn't eschew abstractions, that would be impossible in a broad sense. What he plays with are beliefs that have no basis in reality -- Zap 210 is horrified because she has seen secrets that are forbidden to her by Authority, and she has an appropriate emotional reaction, while Reith is saying that the forbidden nature of this information isn't real, it's just imposed by the Pnume.

Speaking of abstractions in Vance, don't forget the ode to mathematics in Turjin of Miir.