Stainless can be considered both rustproof and rust resistant depending on your outlook.

There are many alloys that are virtually rust proof under normal land based conditions. Rain, snow, UV, air pollution, etc. will, not cause rust in both the short and long term. What makes them rust proof isn't consumed any more than your skin is. However, the right conditions, ie. chlorides, or other chemicals, contamination of the surface with other materials including iron, or other not normal conditions can make these vulnerable to corrosion, some of which may be rust, some not but equally destructive.

So, your bike cables or spokes may be fine and rustproof on a bike, but only rust resistant if the same alloys were used on a ship.

By way of example, I have bikes in Cozumel, a place with one of the most chemically destructive atmospheres.

So, both bikes had stainless steel spokes originally, and within 2 years both had the spokes compromised by chlorides, and as brittle as uncooked spaghetti. I chalked the damage to spokes that were improperly "passivated" and rebuilt all 4 wheels with new spokes. That was over 10 years ago, and there's no hint of problems. At the same time, all the original cables, both stainless and galvanized (zinc plated) are OK also, though the stainless ones still look new, and the galvanized ones are almost black.