The internal ReplicaSetMonitor has capaiblity to remember the seed list for any replica set that it has talked to. This is so if replica set times out for some reason and the monitor is removed, and a subsequent request comes again for a host from this replica set, if will be able to remember whom to contact even if the replica set has changed underneath.

This functionality neither makes sense nor is necessary for the usages of the internal client, so it should be removed.