As part of the implementation of the explain command on mongos (
SERVER-14102), a stub Strategy::commandOpWrite method was put in place for targeting write commands. Currently this method simply delegates to the existing Strategy::commandOp(), using an empty BSONObj as the targeting query (refer to the code here).
The implementation needs to be filled in to correctly follow targeting rules for writes. Currently the stub Strategy::commandOpWrite() is only used for explains of write commands, but this means that explained write commands will be targeted incorrectly.