Of the two Dexron VI bottles Ive seen, neither claims to be a full synthetic anywhere that I could find. An while I'm on the topic of Dex VI, I wanted to mention that Wal-Mart has there own DexVI now for >$3 a quart. Bout half the price of the other DexVI's Ive seen.
An before anyone rags on "Supertech" I started using the DexIII stuff after a local recommended it telling me how cheap it was an that he had changed it yearly on three vehicles using SuperTech DexIII all with good experiences. Thats no proof of anything but if the DexIII has treated me an him both well, I see no reason not to believe the VI would be good as well. An at about half the price of the "name brand" stuff its cheap preventative maintenance to change.
As far as your opinion on synthetic tranny fluid, I agree, but only on new rebuilds or new trannys. I'm against switching to synthetic once it has a fair amount of miles on it. Ive read to many peoples accounts of switching an then describing it as being "too slick" for the trans to grab.
Also after reading your post I went an found where Dave talks about his own mix an I would be willing to try that as well. Even if I had to buy 5gallons. But it sounded like he could ship out his special 5 or 6qts of special blend an then we dilute that with DexIII in a 5gallon bucket. I'd even wanna try his mix with diluted with DexVI see if we cant make the perfect fluid
PS. Here is the thread that Dave talks about this fluid a little bit. What Tranny Fluid Should I Run