There have always been Pentagon brass not on board for a pullout, among them Gen. Frank McKenzie. Today, the general downplayed the idea of a pullout, saying the Taliban had yet to meet certain conditions.
Broadly, this is based on allegations of al-Qaeda being in Afghanistan. That’s being pushed by the Ghani government, itself no fan of the pullout.
Vagueries in the deal were always seen as providing pretexts for the US to slow or stop the pullout. With the US ahead of schedule it is only now that doubts are growing.
Still, President Trump has advocated the drawdown, and until that changes it is unlikely that this will be any more than talk.