Dexron-VI ATF is specified in the owner’s manuals for 2018+ Enclaves, which use the 9T65 transmission. There is a Dexron-HP (High Performance) fluid, used in situations where low temperature fluidity and potential fuel economy are priorities (according to GM–note this may apply to both VI and HP), and that was first used in 2018 in the 9T50 transmission (according to Wikipedia). Perhaps this is the “new” fluid that has been mentioned above. It is supposedly backward compatible with Dexron-VI (but don’t take my word on that). Just doing a drain and fill with the new HP fluid may not get enough of the new fluid in the trans to be an advantage. A full exchange would be required.