Biden did not have to follow Trump's timetable.
Blinken is pretty useless, but could probably be counted on to tell the Taliban that the time was pushed back. Recall that the moron, Biden, thought that a pullout on 9/11 would be some sort of symbolic victory? What a joke.
Furthermore, his administration was awful in terms of coordinating with our fucking NATI allies. Just inexcusable all around.