The Metro system outgrew what it was circa 1980 and hasn't really caught up with itself. Everything used to end at Embarcadero and there were no loops or crossovers, so station platforms were simply labelled "Downtown" or "Outbound." Then the lines started going beyond Embarcadero starting in 1998 with the extension to Caltrain. Then we got the T Third Street extension in 2007. At that point the old convention stopped making sense, and I completely agree with the confusion.
