Graduated Spin
It is called on my Miele, and yes it prevents suds lock and or more water from being extracted than the pump can handle. Many Amercian front loaders simply start the final spin cycle, then if sensors detect suds lock and or too much water slow the spin down until the situation corrects itself. Trouble is if the situation does not change, machine never reaches final spin speed, and one is left with under extracted laundry.
On one's Miele, another advantage of the graduated spin cycle, is laundry is redistributed several times before final high speed spin (if chosen), thus much less chances of an unbalanced load.
As for the merits of impeller washers, have been there and done that with the Hoover. While the desgin is different, still they aren't my favourite design. Too much tangling.
L.