You are correct (and I was mistaken earlier); setting the AVR to 6 ohms as opposed to 8 ohms *does* result in a lower power draw by the amplifier and is intended to counteract the power draw tendency of low impedance speakers. I misinterpreted this menu option as measuring the amp's power resistance. You are absolutely right that the toggle is a power saving and overheating risk mitigation feature. The unintended consequence of using the 6 ohm setting on the AVR is potentially diminished sound quality.
All of that said, the power saving benefits and lowering of the amp's internal temperature are appealing to me. I've not noticed any discernible decline in audio quality when using the 6 ohms setting as compared to the 8 ohms setting. I encountered the same audio issues at both the 6 ohms and 8 ohms setting during the first couple days of use.
I will likely change the setting back to 8 ohms at some point this week for observation purposes. I will then report my findings here.
This advice (from one of the URLs you linked) makes sense to me:
The best setting is to leave it at the 8 ohm or higher setting, as this will make all the power the amp available. However, if it results in the amp going into protection mode then you will have to lower the setting as you're stressing the amp enough where it overheats. Also lower the setting if you feel uneasy since it is related to product safety.
I think the protection circuitry is what might explain the power cycling on my Yammie before it hit the skids. Regrettably, I have no recollection if it was set to 6 ohms or 8 ohms recently. I do remember playing around with that setting after I bought my current front L/R speakers a little over a year ago. With my former speaker set, I also remember playing around with that setting, and I do recall hearing some distortion when using the "6 ohms" setting, so for those speakers, I know for sure I returned the setting to 8 ohms.
Morgan Wallen is a piece of garbage.