While this will initially increase the efficiency of balancing, it is not without a negative side-effect.
Older nodes in a cluster will slowly filled with smaller blocks as time goes on. This is accelerated if the cluster is heterogeneous. The smaller nodes will fill up more quickly/frequently and the balancer will move only big blocks out of those nodes. As more balacing happens, those nodes will contain more and more small blocks. If sufficient time passes, the blocks on those nodes will almost entirely small.
This feature can be enabled for quickly resolving a storage balance issue, but long-term use can have unintended side-effect. Fortunately, we have not released any (other than alpha) with this feature. We can include more information in the release note and/or address the issue in the code/config.