Thank you for clarifying! I did not know that all functions in Haskell are considered curried. My surprise stemmed in part from reading a bit about "arity" from [1].
It's interesting how the theoretical model of Haskell--"all functions in Haskell take just single arguments"--differs from implementation, where, for functions of known arity, GHC in particular does not actually "follow the currying story literally" [2].
You're absolutely right to point out that implementations and theory often differ; compilers often do tricky things behind the scences.