No, they would still count as 1 session, just that session would span multiple areas.
You are trying to reconcile two different things. 1 session/visit can span multiple pages/areas. 100 page views does not mean you had 100 unique visitors. A visitor can view multiple pages.
What you are looking at is simply telling you how many visitors visited each area. Adding the numbers together from each forum will always be more than the number of unique visitors unless each visitor only visits one section. If one visitor visited each and every forum, you still only have 1 unique visitor/session, but each area had 1 visitor from that.