This is a classic example of a technical solution to a training problem. The loaded chamber indicator was obsolete before it was invented, because Jeff Cooper had already invented RULE #1: “All guns are always loaded.”
If we follow Rule 1, we could call it an “empty chamber indicator” but why would we want to put our faith in a mechanical gadget when we can confirm the state of the weapon with a much more exact manual procedure? (Check condition of readiness or “press-check”) I know that no gun manufacturers were clamoring to add this “feature” to their guns but were forced to either by contract requirements or gun “safety” laws.
This is one of the most dangerous safety features I can think of. By creating a mechanical widget (that can fail) for people to depend upon instead of good gun handling like Rule 1, situations become more dangerous. If Rule 1 is followed the loaded chamber indicator is irrelevant, and if Rule 1 is ignored then we are putting a lot of faith in a spring-loaded little nub.