I am flying EWR-CLT next Tuesday. Yesterday morning (T - 5.2 days), there were 4 FC seats open. At T-5 days (almost to the minute), I was upgraded. When I went in to pick my seat, ALL 4 previously open FC seats had been filled. So, no chance to change seats. All 8 out of 8 were filled at the T - 5 day mark.

So, I can't see where CO is holding seats for sale, at least on this flight. Not even one was held for a B-up.