Stage restriction differs between untyped and typed TH

File:

{-# LANGUAGE TemplateHaskell, TypeApplications #-}

module M where

data T
x =  $(const @_ @T  [| 'a' |]  undefined)
y = $$(const @_ @T [|| 'a' ||] undefined)

x is rejected:

    • GHC stage restriction:
        ‘T’ is used in a top-level splice, quasi-quote, or annotation,
        and must be imported, not defined locally

But y is accepted. Is there any reason why untyped and typed TH behave differently?

I don't have any example where this actually goes wrong. If there's a reason, it might be added to the documentation.