Less drying flavours & the associated flattening of acidity.
From the start of extraction, the flavour balance generally goes (as you/the machine pour more water):
Oily in the start,
…then to sweet & gooey,
…then to sour/tangy,
…then a little dry/bitter spot,
…then to balanced clean flavour,
…then to flatter acidity/more bitterness,
…finally moving to full on drying/smokey/sickly astringency.