Your explanation(s) of it is one of the best I’ve run across in a web forum discussion of the topic.I dont think any of this is news to you
That condition is called the mixed mode regime. In a journal bearIng you want to maintain a full hydrodynamic regime where HMIN is never less than the height of the asperities and there is no metal to metal contact.
HMIN is largely dependent on the radial loading on the journal, the rotational surface speed of the journal relative to the bearing, diametral bearing oil clearance, and the dynamic viscosity of the oil.
Slow engine down HMIN decreases and you get boundary conditions
Thin oil out with heat or loss due to hydrodynamic shear force HMIN decreases.and you get boundary conditions.
Lug (load) engine up at low RPM HMIN decreases and you get boundary condtions.
And the nail in the coffin. Over tine bearing clearances inevitably increase with wear, HMIN decreases during nornal operation, boundary and mixed mode lubrication begins to occur more frequently, and the rate of bearing wear accelerates.
I’ll offer up to those that have a belief otherwise, that this explanation happens to be a mathematical model of the behavior. It’s not a faith based belief. So if math isn’t person’s thing, it’s ok, but the phenomenon described by the model will continue regardless of one’s belief in the model. E.g. planes will continue to fly and engines will continue to wear even if a person doesn’t understand why.