In two separate games I've claimed territory (cities and their attached territories) during a war but the expansionist star count as not updated. Taking any other action to adjust the count (such as detaching a territory and re-attaching) will fix the issue and count the territories that changed hand in the war, but it does not seem to automatically update otherwise even after several turns.

Screenshot for reference. I control Harappa with one attached territory giving a count of 2/3 for the star. I just finished a war and took Kerma which should give me a total of 3, but the count still say 2/3 and the star is not awarded.

Next, I attach another territory to Harappa. The count is now 4/6. This count includes the territory I just added as well as Kerma. However, I should not have had to take additional action for Kerma to count.