As initially reported in #8486 (closed), base does not export Typeable instances for its promoted data constructors, as witnessed by this:

{-# LANGUAGE DataKinds #-}

import Data.Typeable

x = typeRep (Proxy :: Proxy True)

yields

    No instance for (Typeable 'True) arising from a use of ‘typeRep’
    In the expression: typeRep (Proxy :: Proxy True)
    In an equation for ‘x’: x = typeRep (Proxy :: Proxy True)

It is indeed possible to derive these instances locally with standalone deriving, but that seems very problematic, should multiple modules do that independently.