There is no need for baseless fear mongering. DEXRON VI is the correct viscosity fluid for the OP's transmission.
It's engineering.....not "fear mongering." I'd expect better from BITOG.
The correct viscosity fluid for the OP's transmission is the one the factory engineers designed for it. Back-speccing a fluid
doesn't make it "the best one." You can't have both a 7.5 and 5.8 cSt (LV) fluid both being optimum. It's one or the other.
The marketing dept's of major auto makers have back-specced a lot of motor oil and trans fluids since approx 2000 for improved
mileage (reduced friction)......it doesn't mean those are optimum for the engine and transmission life. They are apparently "good enough"
for mfg warranty life.
For a complete answer to the OP's question we need to know what year that trans was built (in new vehicles from 1993-2012), and the current
rebuild specs. Back-speccing from Dex III to Dex VI on the 4L60 was done in 2005. "No longer licensed" doesn't mean "obsolete." GM initially tried to back spec the manual T56's to Dex VI and realized that "slightly lower viscosity" was a problem. So those cars are still specced for a
Dex III-type fluid.