When you first walk into the arena the war bears can win sometimes. Another thing I find interesting about this lost sector is if you let the thrall chase you in from the cage room and let the waves of fallen and warbeasts fight, the fallen and war beasts will never attack each other. They will team up and attack the thrall but never each other. These warbeasts are classified as fallen. Doing the izanami forge ignited quest step, I was getting blended ether from kill the war beasts, which also supports the idea that they are fallen. This is insignificant but I think it speaks to the intelligence of warbeasts, and that they will simply fight whatever enemy they are pointed towards.