Number of rinses
Means little in terms of rinse-ability. You could theoretically have a machine with 8 post main washes rinses and still have more residue then a single rinse Whirlpool. I know because I've used 3 rinse GE and Dura-wash dishwashers that have left behind more detergent residue then single rinse Powercleans when the cup was over filled.
The low carry over water of the vertical module, post main wash purge which further reduces that carry over, and high water charge (2.2 gallons) offset the single rinse scheme. Most dishwashers that do two rinses do so because there is more carry over water (and often less water per fill ie, 1.8 gallons) thus making it necessary- and dishwashers with the most carry over like GE predominantly had 3 rinses.
In fact GE in the 2000s had models with both a drain solenoid and aux pump. Everything was identical, but the aux pump model (which drained the sump after each solenoid drain) rid itself of one prewash and one rinse. Fill went from the typical 1.3 gallons on the BOLs to about 1.6 on the aux models to offset the water taken from the sump. 1.6 gallons and two fills is about what most other dishwashers did as they did not have several quarts carry over.
