The balancer will not move chunks unless there is at least a difference of 2 between the number of chunks two shards possess. The balancer is doing nothing in multi_mongos2.js because it is only started after manual split/moveChunks are performed that rebalance the number of chunks on shards. The balancer being enabled is unnecessary and prevents multi_mongos2.js from being in the sharding_continuous_config_stepdown suite.