After reading about how Gary Rydstrom went about remastering T2 for the 2000 Artisan Ultimate Edition DVD it turns out I'm completely wrong about the whole thing. Disclord mentioned:

The first T2 DVD of the theatrical cut from Artisan uses the same 5.1 channel mix that was prepared for the 70mm Kodak/ORC Cinema Digital Sound prints

After reading the interview with Rydstrom it turns out the CDS mix was referenced in the 1993 Dolby Surroung laserdisc LD68952-2DD and later reused as the source for the 1998 Artisan/Live R1 DVD 5.1 Dolby Surround track. Rydstrom took it a step further for the 2000 DVD and remixed the audio to take advantage of the Dolby EX format. So, straight from the man’s mouth Rydstrom confirmed the CDS mix was in fact the source. I apologize for the confusion!