It's useful for choosing your flow and saving on battery and pump wear, but...
Mine makes it's own decisions all the time and it's annoying.
I set a steady flow, then a few moments later it's blasting out, using all my water and battery.
So I go back and turn it down to a nice pace, then minutes later it's a dribble.
So, turn it back up...you get the picture.
Yes it certainly "varies" the stream!