Actually air cooled two cycle oils dont have dedicated rust inhibitor packages. They contain some calcium or magnesium based detergent that does have some buffering capacity to neutralize combustion by product acids. I wouldn't trust any of them for more than 6 months in a damp climate. Ester oils like like K2, Dominator, R50, etc are particularly less robust at corrosion protection. This is because they use ester base oils. Esters have great biodegradability, which means they breakdown in the presence of air and water. This property also makes them less robust at protecting from corrosion.
Regardless of oil used a guy shoukd use fogging oil when storing s two cycle. Its cheap, available st Walmart and takes seconds to fog chainsaw. After having expensive motor rust on me years ago I started using it and have ever since with perfect results.