PAO based fluid flows better than Grp III and Grp II at very low temps.
MIL SPEC 46167 is a PAO based 0W20 developed for engines and transmissions to cold startup at -60F. (Basically this was anticipating fighting the Soviet Union in Alaska or Siberia during the cold war.) We tested it a lot at Allison in military transmissions and it works as intended.
But unless you're talking temps like -30F and below, it's not a big concern.
There were a lot of Grp III based Dexrons that worked fine on -40 startups.
However PAO's also are more oxidation resistant which is beneficial if your system runs at high temps and/or you want long service intervals. The performance requirements of Allison TES-295/668 pretty much requires a PAO base if you're looking to find a Dexron type product.
