Clojurians Log v2

hi all, here's an interesting one to all of you schema gosus:

(type (first {:asdf "asdf"}))
=> clojure.lang.MapEntry

(type ((schema.coerce/coercer
         (sc/map-entry (sc/eq :asdf) sc/Str)
         (constantly nil))
        (first {:asdf "asdf"})))
=> clojure.lang.PersistentVector

why does the type change during coercion?