I find it odd that VE would be used in open loop but not closed loop. The MAF sensor has nothing to do with the O2 sensors and I don't see why it couldn't be relied upon regardless of operating condition, cold or hot (except a brief period after engine startup).
Open loop fueling should be controlled by the open loop fueling tables, as well as the measured airflow input from the MAF sensor.
This snippet from TunerCat has me thinking:
Under changing conditions where the vehicle is accelerating, decelerating or the load is changing significantly the PCM essentially goes into speed density mode and uses the VE tables to calculate the required fuel. Once conditions stabilize the PCM goes back to using the MAF sensor readings. I believe this is done because the MAF sensor are relatively slow to react to quick changes in air flow.
If this is true, then it doesn't matter if the PCM is in open loop or closed loop mode. It still needs to calculate AE fuel when required.
Of course, TPI cars from 85-89 come to mind. They had no MAP sensor. But they had explicit AE tables, whereas LT1s don't seem to. So once again, they've either not been found by the makers of LT1edit and TunerCat (after how many years???) OR the PCM calculates AE from something else, like VE.
Or that's all wrong and it DOES use the MAF for AE. Doesn't seem like it would react fast enough. The engine kinda needs fuel the moment the throttle is cracked, not moments later after the pressure wave registers on the MAF element a foot down the intake tract.
I may still experiment on my car...