They must mean Hemisalanx brachyrostralis . Like I said, the common name for "silversides" is often applied to any small fish with silvery colored sides, including some species of smelt. Hemisalanx are related to true smelts. Some smelts have thiaminase. Some do not.

SF Bay Brand and Sally's are the only brands that I could confirm as being Hypomesus olidus, which is a species that does not contain thiaminase.