As I discussed before, I made this list to reflect the continuity as it would've been seen in the '80s, before TNG came along and changed things. The idea was to offer a glimpse at a period of history, to try to codify an old interpretation of Trek continuity which has since been superseded.
and The Empty Chair
came later and retconned some TNG-era ideas into the Duaneverse, so they represent a different era's take on the continuity. After all, the revised versions of the earlier novels as found in The Bloodwing Voyages
retcon them to be post-TMP rather than in the conjectural "second five-year mission" implied to exist in the original version of the books. Swordhunt
claims to begin two months after The Romulan Way
, but is also after Spock's World
, so that definitely conflicts with the '80s version of the continuity I tried to reconstruct above.