"Any input on my hypothesis that perhaps higher ,less dense electrolyte levels might allow more sulfate to be redissolved into it from the plates?"
Not answering that question as such but related?
Noting how higher volume of "water" reduces the SG reading at "full"
Been wondering why a battery that has lost capacity from sulfation over the years, but still shows proper voltages vs SOC, has lower SGs.
I am thinking the battery is still the same size, holding the same amount of "water," but it now has the capacity of a smaller battery that would hold less water. So when you fill it to the split ring, and de-stratify, it is like your smaller battery being over-filled so the SG is less?
But in this case the stuff is stuck to the plates permanently so can't dissolve into the water to bring the SG up to normal.
In your case the stuff is still soft so if the charging current is still going through to continue the chemical action then more water ought to hold more stuff--but wouldn't that just leave the SG the same since the ratio of stuff to water is the same? To get higher SG you need it more acidic. Water level shouldn't matter since you could just "overcharge" to get more stuff in however much water and get more acidic that way.