Well, at least in Economy, all fare buckets can be issued at least as SL,KM or KD.. for instance if you go to ITA Matrix you can force VLESLZ0B ,VLEKMZ0B or VLEKDZ0B on a oneway fare SCL-MAD in FEB. What is crazy is that you can have a full fare Y fare bucket and then no bags, seats or flexibility if it's Light (SL).