A feature to accomplish... what? It isn't "autocomplete" as the original title implied; the .s never appears in the save dialog even if you tab away from text

A feature to accomplish... what? It isn't "autocomplete" as the original title implied; the .s never appears in the save dialog even if you tab away from text entry. Apple has been deprecating global access to the universal type system, so it is certainly possible this was an edge case falling out from that.