The activity Synced, but the Rank didnt. Is it supposed to be like that? He deleted all previous posts, so that his post count went down and the activity too. But does the rank stay at the highest you have achieved no matter how much activity you have lost?
This is exactly what I think happens with this forum. Although the activity levels drop, I don't think the system will automatically demote users to lower ranks. However I'm sure an admin could manually change his rank to Member now, because he should be ranked as one with that activity.