With the Andorian warship I kept expecting someone too say that it was one that the Andorians had pulled out of mothballs from over 200 years earlier and just upgraded, but no one said anything (just how long were the Andorians planning on seceding from the Federation). And I don't get how the Andorians could've built new warships without Starfleet knowing about it. The Historians note says that the story starts two weeks after the secession, but the Andorians have fully constructed warships, even though Starfleet would've had a bases and starships in the Andorian system upto the withdrawal; I doubt that the Andorians would've needed a space fleet when they had Starfleet. And the book takes place over the course of no more than to weeks.
The Andorians did have a defense fleet when they were in the Federation. Paths of Disharmony
said that half the fleet was destroyed in combat against the Borg, the Therin
presumably belonging to the half of the fleet that survived.