The problem with a POW label is that indicates a war between 2 different countries. Taliban is classified as a terrorist group and not a government.
From ABCNews:
But Tuesday White House National Security Council spokesperson Caitlin Hayden noted that the Taliban was added to the list of Specially Designated Global Terrorists (SDGT) by executive order in July 2002, even if it is
not listed as a Foreign Terrorist Organization (FTO) by the State Department. Either designation triggers asset freezes, according to the State Department, though they can differ on other restrictions imposed on the target organization. The Treasury Department told ABC News the Taliban is still on their SDGT list.
...
Though the State Department has not designated the Afghan Taliban as an FTO, it has designated the group’s sister network, the Pakistani Taliban, as well as the Haqqani Network, a group closely associated with the Taliban that was believed to have been actually holding Bergdahl for most of his captivity. Hayden told ABC News the U.S. “did not negotiate with the Haqqanis” for Bergdahl.
Rather than arguing the status of the Taliban, however, the administration has launched a coordinated effort to characterize Bergdahl as a prisoner of war, rather than a hostage.
“Sgt. Bergdahl was not a hostage, he was a member of the military who was detained during the course of an armed conflict,” Hayden said. “The United States does not leave a soldier behind based on the identity of the party to the conflict... It was a prisoner exchange. We’ve always done that across many wars. With the Germans. The Japanese. The North Koreans.”
As President Obama put it earlier Tuesday, “This is what happens at the end of wars.”