There are almost never any problems using a SWG with a metal frame/panel above ground pool. However, the loss of warranty coverage is an issue with most brands that is worth consideration.
The main risk is that the liner will leak onto the frame and you won't notice, allowing the frame to get wet and stay wet for an extended period of time. In those conditions using salt water will slightly speed up the corrosion of the frame (which will happen anyway even without salt in that situation).
Across thousands of members, we have only heard of a couple of pools where the frame rusted through, and in those cases it is never clear that it wouldn't have done the same thing even without salt.
By frame I mean everything involved in holding up the liner: uprights, top rails, and walls. Obviously, the less metal in your pool, the less risk there is, but the risk is low to begin with.