FWIW, I'm far more interested in finding the (detailed) truth about such topics as these than being right. Not interested in arguing, just trying to understand.
In my mind,
You cannot change the ratio of premix once you've mixed it. Typically Factory Specified.
You cannot change how much fuel/air the engine requires to idle. A physical aspect of the engine.
These will be constants, whether the throttle is pinned or the throttle is shut.
Idle will receive the same volume of oil per volume of fuel as WOT.
Only the engine speed changes. The throttle opening increases the flow of fuel/oil to accomodate the faster spinning engine.
Typically if an engine dies at idle or ''loads up" then it is too rich, not too lean. Too lean would cause an increasing idle or hanging idle. This rich condition means extra fuel is spreading extra oil to the essential components. Probably a good thing.
Now where the dangers of idle throttle oil provisions are dangerously low would be shutting the throttle completely from a WOT top end run. The engine is still at max rpm with a shut throttle (Idle fuel/oil). That to me is FAR more dangerous then letting a bike idle for a minute or two.
Discussion! I refuse to just say, "oh, i heard it from so and so..." We have enough of that in our govt today.
-BIG DAN
EDIT:
Another HUGE part of engine life, and why the thing needs oil in the first place, involves engine LOAD.
At idle there is very little load and a ton of residual oil all over the rotating components. I think the engine would need exponentially more oil while under a heavy load.