For indoor work I guess the top jet is used just for minimal fine misting enough to mop it with micropads not get it so soaked as you would do when doing external cleans.
For exterior work the concept for a top rinse bar goes back donkey years to the when wfp was first used on commecial jobs.
Did not matter what type of brush you used as would rinse as you brushed the glass all in one so no extra rinsing was required saving time and effort.
Now for some reason the likes of wagtail and many others have brought back the concept of one pass wfp cleaning using a rinse bar attached to either a pad or brush.
Most mono filiment bristle brushes you can get away with rinsing on and some even do a one pass on regular cleans. However flocked bristles the ends are split so not only gives more contact to the surface you are trying to clean but tends to trap crud in between so you need to either rinse off or use a top rinse bar.