Hang on, I've eaten there! (This is the First lounge below the Concord Room, not the Terraces lounge.) There's a menu, there are tables, and there is wait service--I'd call that sit-down dining. The food's not bad, either. I've never been asked to show any proof of an F ticket--I am always a Gold interloper there.

The experience was a lot more rarefied at the First lounge at JFK the one time I went through there when I had a promotional upgrade to F, but still, a menu and personalized table service to me does equal sit-down dining.