It's interesting, from what I can find, when 'Cookmatic' was introduced, it was referred to as the "Cookmatic Power-Shift". If you wanted analog controls, you could buy an RR-7. If digital, an RR-9. Both had the variable slider, or "shifter".
I believe the 'Power-Shift' terminology was dropped when Amana realized they could just integrate the function into the control pad on the digital machines (thus, the 9T and 10). You still had the levels, and they stamped 'Cookmatic' on it.
This also appeared on the analog RR-8/8A, but never on the mechanical defrost machines. However, the 80's rolled around and maybe they were getting desperate, because all of a sudden they stamped 'Cookmatic' over the window of the RRL-5C and 5D. There's nothing variable about those models, but there you go.