Older SOGs had polished handles and really early SOG pliers heads were polished. Starting around the time SOG moved production overseas, the plier heads were finely machined(ground) and looked "shiny", but that isn't true polishing. Throughout, some implements had a high polish, with exception of a few implements(ex. Phillips) that are finely machined(not actually polished).
Theoretically, the "stone wash" finish should be more resistant to corrosion than a finely machined finish. A machined finish, which is essentially a "grind", which has thousands of peaks/valleys when viewed under heavy magnification. The stone wash has a fairly even surface and will prove more rust resistant than a "bead blasted" or "satin" finish.
The handles on the newer tools not being polished shouldn't be an issue if you keep the non-used surfaces oiled a couple time a year.
High polish has no equal in corrosion resistance, but most other MTs have a satin/bead blast/etc finish and hold up well anyway. So, a high polish isn't exclusively corrosion resistant. Steel type plays a big role as well. Tools with high polish can and do develop rust without care and oiling.
The SOG stone wash finish is NOT a bead blast finish. It is what it says it is. The parts are tumbled with slightly abrasive stones to achieve the "stone wash". This also smooths the edges as well.
I imagine the steel is similar in composition to other SOGs, but since so many people put too much importance on the "type of steel" instead of the "type vs. what it is for", SOG may not want to put it on their site(or someone didn't know). But, if asked politely, they would probably find out for you.
Edit: don't forget the biggest problem polished handles have. It is slippery. The Stone wash feels a bit less slippery in the hand.
SOG still makes the PowerAssist and PowerLock, so they aren't really replacing the old styles, but they seem to be trying to get in on a different MT user market. The "cool"/"tacticool" style started in the PowerPlay, but has evolved to the nice style we see on the Access.
You want the polished SOG tools? You can find them for sale everywhere.