I would never called it an "ECO mode". In his review of the 7100, Amir called it a "limp mode" which is much more proper.
This is how I see the 2 modes as defined:
ECO mode - an "on purpose" mode (can either be defeated or not based on manufacturer spec) whose sole purpose is to save power and be "green" during idle conditions or periods of low power demand. Does not require unplugging of the AVR to reset.
Limp mode - an unfortunate fail-safe position that limits the capability of the AVR such that it cannot cause damage while operating in an "unsafe" state and has nothing to do with power economy. In the case of 2021 Voxx products, this state will be triggered by low impedance speakers/loads and the AVR
MUST BE powered off to be restored to prior default state. Anyone who has ever experienced "limp mode" in a car knows that it takes quite a bit of effort just to get the car to the shoulder. No one would ever confuse this limp mode w/ECO mode for boosting fuel economy!