Interesting information
If the heater operated during warm rinses after the warm fill, what would the temperature have to be to trigger water heating, i.e. how much less than 100F and would the one minute rinse period be extended through a timer delay to heat the water to 100F or was the heating mandatory on the warm rinse setting? I can't imagine a house with such a meager hot water supply that at least warm water could not be supplied for rinsing. Each fill in this machine only took 3 gallons of water after the load was saturated. If the heavy drum and the load of laundry were already heated up to warm, medium (120F) or hot (140F), it would be hard to see how 3 gallons of rinse water would drop the temperature enough to require heating during the first rinse or two. Maybe by the third rinse, if the hot water supply was exhausted and all that was coming through the line was tap cold water, heating might be required, but this seems highly unlikely. Granted, with the high wattage of the immersion heating element in the electric machine, the water would be heated quickly, but it seems very wasteful and with only one minute of rinsing from the time the water level pressure switch was satisfied until the drain valve opened, it does not seem like the heating would serve much purpose except to keep the drain lines warm. It was, however, the late 50s and excess in appliance features was the watch word of the day. Even Bendix, which had the water heater in the early 36" electric Duomatics did not think about heating rinse water.
I wonder if heating the rinse water lasted beyond the 1957 model. By the time CU tested combos, I think they were testing the 1959 models and they bitched about the high cost of the amount of energy comsumed by these machines. They went into detail about the wash water heating of the WP and LK combos, but if these two models heated the rinse water, it must have not been noticed by them. If the gas model also heated rinse water, it seems that they would have noticed that huge 37,000 BTU burner snapping on and off during the rinses. The BOL model I had did not have the water heater, but if you wanted a really hot wash, you washed and dried a load and then, no matter what the wash or rinse temperature was, when the drying stopped, the whole machine was hot so you had plenty of heat to be absorbed by the wash fill of the next load.