Your logic is a fault here. You can say, "The A.O.K. 11 took fewer prisoners than either A.O.K. 6 or Pz.Grp. 1." What you said seems to say in the quote is that an army's performance is judged by the number of prisoners taken.
A.O.K. 11 performed its missions competently. I don't remember any rebuke given it for slowness in carrying out its orders. Being an all infantry army, it didn't have the speed to form large pockets of the enemy. The army missed out on both the Kiev and Uman encirclements and that is why its number of prisoners taken is lower than other armies.