I think it's just meant for those threads that are basically permanent.
A popular game has an OT that can last years, or through multiple instances.. same with this thread.
Keeps the main thread list more about news.
Just need to keep reminding people they are there, and to check the sub-section.
The actual descriptions are...
Gaming: Video game news, industry analysis, sales figures, deals, impressions, reviews, and discussions of everything in the medium, covering all platforms, genres, and territories.
Communities: Ongoing gaming |OT|s, matchmaking, community threads for specific interests
IMO communities by description seems to more a place for OTs, LFP/LFG, and off-topic non-gaming interests (Manga, Movies, Anime, etc for example).
The actual talk about games with tweets, articles, etc happens on Gaming... everything related to Gaming should be in the gaming section and that makes the OT and LFP/LFG being in another place weird.
Edit - BTW using the descriptions Off-topic now makes no sense... off-topic talk should happen in Communities.