No, it should split in the column browser but it currently doesn't show each individual tag's existing sort composer value. As the result, it shows two values for composer tag but four values for sort composer tag.
Another request is its main panel sort composer value should be, again, the existing sort composer tag of individual composer tags. So this case I'd like to see either "Liszt, Franz" or "Liszt, Franz; Verdi, Giuseppe" when its own sort composer tag is not set, no matter what the display composer value may be.