not necessarily. One can spray water in directions that it wouldn't go normally.
Another member had removed/deleted the window washer nozzles. one of those open screw holes allowed water to drip directly into the vent box. Point being rust holes aren't the only holes. If there was a way to pull outside air to interior from somewhere else and delete the cowl vent grille, that's what I would do, along with adding a cabin air filter.