At present, the Taliban have honored the deal to not attack US forces.
Biden cannot further embolden the Taliban by signaling that the US has already been defeated, and making the Taliban think they no longer need to honor any rules of engagement deals.
The situation on the ground remains delicate. Biden could not show weakness or failure.
There will be ample time down the road for a full throated “The Buck Stops With Me” mea culpa re the mismanagement of the withdrawal and the betrayal to those Afghans that we had a moral obligation to protect them.