Of course it matters! That’s the shaky foundation for all these “Trump was acting like a mob enforcer” posts and reasoning. They all assume Zelensky knew that Trump was withholding the money (or Javelins in some tellings), and so Trump’s “I would like you to do us a favor” is supposed to have an ominous ring to Zelensky like a mobster’s “It’d be a shame if something happened”. If Zelensky doesn’t know that he’s being extorted (because he in fact is not), that perceived ominous tone evaporates.