> But with proper static typing you don't have to check it because you already know it's correct since it's construction.

Its construction is dependent on it conforming to a specific form. In this case, your statically typed data comes from a parsed string that is then conformed to a specification to ensure that is has a certain shape. In Clojure you would just do the conforming to specification part and keep the data generic.

I think the appreciation for generic data has to do with the fact the fact that it makes Clojure code very generic and facilitates a lot of functional composition.