They are there because with the HF we have only 1 payout now, and the promotion tab uses the longer from the past 2 payouts system (30 days). The new posts are only there for a week. The old ones will disappear soon (HF+30 days).
Which is great, that anyone could promote a post until the payout. That was only 1 day in the past, and 1 week now, which is an improvement IMO.