This is largely to address item shortages, especially in long games, or after mishaps.
Like the “AI director” in Left4Dead, the game would tend to drop items within reach of the players, things that they need. Ever play that? The AI would make varyingly difficult attempts yo kill you, but when the players were damaged or low on ammo, or items, those items would show up more than they would otherwise. The game didn’t TELL you it was being nice, it just made things available in the spawn locations.
For SD, the storms are a perfect excuse to drop things off on islands. A few palm leaves, logs, or occasionally plastic debris with better could wash ashore. And if not picked up, maybe the items “expire” by being carried off in the next storm if not picked up and stashed.
So if a player is getting really short on fiber, a bunch of palm leaves could show up on various islands during a storm, for example. Or if the player just can’t find one component they need for something, extras could be spawned in. Extra raft floating things, etc. Especially if the player lets some drift off the map, perhaps accidentally.