Mongo shell 3.2 has different results on sh.isBalancerRunning() as mongo shell 3.4
The difference is that 3.4 balancing work is done by config server primary and at 3.2 it was done by one of the mongos services.

To prevent "older" (&lt;3.4) mongos services to start balancing work, config server (>=3.4) makes "lock" document to the local collection, what "states" that one of the mongos services have "balancing lock" set.

That document doesn't prevent (>=3.4) config server to do balancing. That is the reason why older mongos "report" that there is always balancing ongoing!