I again disagree and I don't know what you insist on (a) fighting (b) here of all places; IMO Dexron VIs also shears down as the very high molecular weight molecules are thermally destroyed and otherwise broken down into smaller molecules. Here's an measured example contradicting you of it going from 6+-1 cSt down to 5.6 cSt after 43k miles.
https://bobistheoilguy.com/forums/threads/dexron-vi-43k-miles-on-fluid-6l80e.354573/ Yes, if oil is used long past when it absolutely needs to be replaced, it should oxidize and turn into a new product, a solid gel full of oxidized carbon called sludge, but if the user is at all diligent, this side of the curve should never be experienced, so for all practical purposes (at least for most users reading this site), the viscosity should go down with miles, not up, for all Dexrons.
"This is every bit pertinent to the discussion." OK but I had thought the purpose of this thread was to know how shifting feels as a function of
ceteris paribus ATF viscosity (meaning that only viscosity is being changed and all other things like friction modifiers, oil oxidation, color of the oil, etc., are exactly the same). There are a million threads on the net about peoples' favorite ATF shaggy dog stories, but I was hoping to have one by smart ppl just about this and nothing more. But, what would I know.