I would say that the answer depends on the coping (the type and quality of the stone) and that any coping that has signs of damage in a non-salt pool environment with typical salt levels of 500-1000 (an pool with a fresh fill and initial chemical additions has around 250 ppm) is probably going to see more or faster damage at the higher salt level of an SWG pool (around 3000 ppm). This can be mitigated through sealing of the stone.

You can do a water bead test for your stone. See how long a drop of water stays beaded up on the stone vs. getting spread and absorbed. If it's just a few minutes, then it's a very soft stone and will degrade rather quickly and should be sealed to prevent that. If it's 5-10 minutes then this is still somewhat soft. If it's 10-30 minutes, this is moderately hard, if it's 30-60 minutes this is a hard stone and more than an hour (if the water doesn't evaporate before then!) is a very hard stone that shouldn't need sealing at all.

There's a thread in the China Shop that explores this issue technically, but I don't want to scare you off from an SWG as most people are very happy with their systems. Stone naturally degrades and soft stone degrades faster so should generally be sealed and that is independent of the type of pool you have. We have textured concrete hardscape and concrete coping that we seal every year and our pool doesn't have an SWG.

Richard