On replicaSetPingTimeMillis, we pipe it from here for every host we know about. However, IsMasterRTT is in Nanoseconds and replicaSetPingTimeMillis is in Milliseconds. Thus we can get 0 values consistently for colocated hosts and never represent certain hosts in FTDC. Thinking towards the future, we tend to represent time types in floating point for external users, and using floating point here would also make this clearer.