The earlier post was meant to explain that many Confederates listed as captured at Franklin TN on Dec. 17th were not part of the reteating Army of Tennessee. A large majority of those captured had been wounded during the battle of November 30th. A few may have been sick or wounded between that date and the Battle of Nashville.
As you mention, Confederates wounded and left behind after the fighting of December 17th would have been sent to one of the hospitals in Franklin. However, relative to the large number of casualties already housed there, the count would have been small.