I guess I got the wrong impression. I had read this:
https://forum.mattressunderground.com/t/ultimate-dreams-vs-aloe-alexis
and this:
https://forum.mattressunderground.com/t/memory-foam-toppers-do-any-good-ones-exist
and specifically this:
“the only significant reason to choose one layer of latex over two IMO would be either budget, because someone was lighter and/or a back or stomach sleeper that didn’t compress much more than the top layer and wouldn’t “feel” the deeper layers as much…”
Re-reading it, I guess my takeaway is that, because my wife and I are side sleepers, 6" of latex is better than 3".