yeah headline not the best. Should be "Time not a friend of sellers" or similar. Time kills deals is better said for the due diligence process when offer is accepted.Maybe it just means that overpricing sellers need time to face reality? Not saying that your hypothesis of time killing deals is wrong, but that this might be pointing to another effect.
link - https://www.urbandigs.com/resale-charts/price-/-square-foot/all-manhattan/condo/