Some stainless steel more stainless than others
Yes, there are different blends to make 'stainless' steel and some are more resistant to rust (higher chromium and nickel content), or to pitting (higher molybdenum content) or hold an edge better (eg, 'surgical steel'), but to my knowledge, all of them are prone to pitting if they've exposed to salt water for a long enough period of time.

The exception to this is if the water is boiled before the salt is added, as it's a chemical reaction between the steel, salt, and dissolved oxygen.  This is why many recipes for cooking pasta tell you to wait until the water is boiling before you add salt.

Salt can also speed up the rusting of stainless steel, so it's a good idea to rinse things off if you're not going to clean them right away.  Salad dressings typically contain a fair bit of salt, but it's also quite possible that the bowl is a lower chromium steel.

update: Although there's now another system for grading stainless for the building trades, you'll often see stainless steel sold mentioning '18/10', which is a more rust resistant blend.