I had not considered stratification as the sole reason for this behavior. I remember your tipped '27's, I had some Wallyworld 27 that never required water, and did not stand up long to nightly cycling, though the one delegated to a fully charged engine starter at 2 years, lasted 7 years.
I really try to mix up the electrolyte with a couple vigorous bulb ejections before I bother focusing on the graduations on the float. Perhaps I overestimate the flow and the mixing going on.
I have not noticed any significant water use since I've been using this 31. But I am giving it a few hours of 14.0v plus per day, and do notice bubbling when I check SG while it is still charging in the mid 13's late afternoon.
I have another BlueSeas switch on hand to divert solar from one battery to the other independent of load, I just need to install it.
Once I do that I can perhaps better observe how the just the physical agitation of driving mixes the electrolyte and SG readings under the same recharge regimen, and independent of vehicular load or alternator charging variables