Changed in version 3.2: Starting in MongoDB 3.2, config servers for sharded clusters can be deployed as a replica set. The replica set config servers must run the WiredTiger storage engine. MongoDB 3.2 deprecates the use of three mirrored mongod instances for config servers.
Could it be clarified further, that the config servers deployment steps are different to the previous versions. As if a user would deploy config servers using previous versions they would end up with SCCC. (i.e. scripts, puppet/chef).