In a cycle description I read some years ago, the Pot Smasher cycle extends the main wash into the first rinse to lengthen it. There was not a thermal hold, per se, just more minutes in the main wash on the timer.  I have been told it did a right good job of removing crud and crust, it's just getting the particles out of the machine where it falls down with one less rinse.

In hard water areas you can get quite a mineral crust on the heating element when it runs during drain periods because it bakes on the mineral/detergent film left on the heating element when there is no water covering it, but most machines with a heating element used for water heating depended on the constant operation of the heating element during the drain periods to help heat the successive fills plus it saved wear and tear on the timer from having multiple heater on/off contacts with each water change.