Not too long ago, Shell discontinued the practice of dual rating many HDEOs. This was done to encourage use as primarily intended, and avoid mis-application. Popular grades of Rotella like 15W-40 and 5W-40 rated API CK-4 won't show an "S" rating. Not to worry, they still have the necessary anti-wear additive and perform well in our engines.
30 years ago, Castrol pushed that idea pretty hard in their marketing. They were unable to produce a 5W-30 that could meet API SH, so they scared people into using 20W-50 to avoid "viscosity and thermal breakdown." Remember the commercials with the tach at redline? It was a load of garbage, but it resonated with people and has become part of the oil misinformation mythology.