Well, also: anyone who’s been paying attention over the series [and even in that final episode] can see that Nilfgaard is not a particularly nice power, even compared to some of the other nations in the world. They’re talked about with some dread in Episode 1, and it’s clear that they allow/support exploitation of their populace in ways which are considered “beyond the pale” by other “civilised” countries - see their apparent happiness to have sorcerors literally sacrifice themselves to make big fireballs, and the related tendency for Fringilla to get all “you should totally join us because we have no ethical constraints” as a recruiting tactic for magic users in general.
It’s also made clear at the start of the episode that the bridge that the fortress secures is the most significant route connecting the territory that Nilfgaard has just conquered with the unconquered Northern Kingdoms, so there’s a pretty straightforward reason for the battle to happen where and when it does.
So: yes, the point of the episode on a “personal” level is related to how Yennefer deals with seeing her comrades dying in battle, etc.
however: I don’t think that’s the problem that the author of this piece is having. From context, I don’t think they realised that the battle Geralt is present near is also the battle Yennefer is involved in. You and I both thought that was pretty clearly signalled: the carter who’s transporting Geralt pretty clearly notes that the battle involves Nilfgaard, and names the fortress as the same fortress that we know the sorcerors are at… but I don’t think that was enough for the author of this piece, despite the fact that the previous episode had established that all our timelines were finally synched.