Also, even if one did try to force the books into some contrived "TV season" model -- which would be a rough analogy at best -- I don't agree with the assertion that Unity would be the "season finale." If anything, it'd be more like the big February sweeps 2-parter, with Worlds of DS9 filling out the rest of the season and the end of Olympus Descending being the big cliffhanger finale. After all, everything from Avatar to Olympus Descending (or everything from The Left Hand of Destiny to OD, going in chronological order) takes place in 2376.
So stating as a fact that Unity is the "season finale" is greatly misleading.
I'd disagree, as we have had TV seasons end mid-way through a year, and then the following season continued the one year and went into the next (Voyager's Season 1, while it was a network decision, did end at "Learning Curve", with the remaining 4 episodes being 'shuffled' into Season 2, the episodes even had stardate's starting with '48', while the S2 stardate's were '49xxx.xx'; again in Season 3 we saw some Season 2-produced episodes 'shuffled' into Season 3; not to mention TOS's 3 seasons having adventures from all 5 years of the Enterprise's voyage).
In terms of the pacing of the stories and build-up, "Unity" tends to work better as a "season finale" than "Olympus Descending". The "Worlds Of DS9" books I always found played more as the opening of a new story/"season" than as a finale.