You can liken this to "punching down the cap" in wine making.
Just keep pushing it below the surface to keep the fruit wet/moist, so that it can't dry out. As there's possibilities of flavour issues if it does.
Plus the continues slight agitation of helps to knock any CO2 out of it where the yeast is getting to the fruit sugars, but gets held inside the skins.
People often thing that if they puree the fruit, it will make their lives easier and that the yeast can get to the fruit sugars quicker or more easily. They then find out that it's a complete PITA as the puree will cause a high level of sediment/sludge (oh, and of course, they will have pitted/stoned the fruit first as you wouldn't want smashed or broken stones/pips, that can cause bitterness issues), and the fruit sludge can be a bugger to remove, requiring extra rackings and the consequent racking losses.
Hence it's usually suggested that if you just freeze the fruit, then defrost it before adding to a batch (with all the juice that comes out of it) then the freeze/thaw action will have broken enough of the fruit cells to let the yeast in to get the flavour/colour etc quick enough for the yeast and that it doesn't hold as much CO2 during the ferment, and theoretically at least, should sink quicker.
Plus it doesn't matter about pitting the fruit, though I prefer to where possible.