What a load of tosh. There is only steam within millimeters of the tip of the lance, then it reverts back to water vapour, The instant those micro droplets touch the window they are cooled dramatically. You are advocating using mildly warm water without cleaners to do the job.
I used steam cleaner and squeegie to clean my mirrors and it worked way better than windex. (Previous owners were smokers and using any ckeaner just smeared the tar around.