Giveaway posts are created days/weeks before they go online. Then they are checked from the publisher of the game and if they are ok they go online at a specific time. In the case of the Lightmatter giveaway exactly at the publishing date.
But in the meanwhile its nearly impossible to get a useful gamekey from AWA giveaways because the level cap is too low and there are too many members with high level accounts for a very limited amount of keys.
My personal experience: I missed nearly every game key since I'm Master Level. So leveling up here just for better chances in getting gamekeys is rather pointless now.
Additional Info: This site has cashing issues since last summer. Recent posts are showing up 6-8 minutes after they go online. In the meanwhile they could have fixed this but thats just my opinion.