The WM25 as with all Aquarius models has a low level as standard, super rinse would fill about 2 inches up the glass on my Nana's.
To be honest, water levels aren't important when it comes to rinsing, there are plenty of variables - in my opinion spinning out the soapy water between the rinses is more important. 2 low level rinses in my washing machine on the cottons cycle with faster interim spins always rinses better than the 2 high level rinses on the Minimum Iron/Quick Wash cycles that don't spin as much between the rinses. The Miele I have will spin for up to 4 mins (depending on the load size) at 1000rpm after the mainwash, and gives the rinsing process a huge kick start.
Again, on my Hoover Electron the first two rinses will always be soapy, but as soon as the interim spin has kicked in on after the 2nd rinse the water on the following rinse is far more soapy.
I've found higher water levels on rinses can actually produce more foam; if you select water plus on my machine the first rinse will always be at a lower level than the following 2.
Either way, it's all horses for courses, and there are many more variables involved than just the amount of water, and to be honest with most loads apart from towels I still have adequately rinsed laundry with the standard 2 low rinses and have no adverse skin reactions even with my eczema.
Jon