Increasing the acid concentration increases the rate, so yes it is.
When you measure the reaction, you're measuring the rate of precipitate formation, and that precipitate is elemental sulfur (S8) - which is formed by the intermediate HS2O3-- so what would be the equation for the formation of that in the thiosulfate-acid mixture?
Not like I like arguing with people with more qualifications than I do, but no it isn't.
Fair enough - I was focusing more on the effect it has on rate since that's what the acid catalysed refers to, but in terms of terminology you're right.