Given the following connection-string:

mongodb://admin:password@localhost:27101,localhost:27101,localhost:27101,localhost:27101,localhost:27101/admin?maxPoolSize=200

Obviously, there is an error in this string but it is neither detected nor corrected by the Node driver.

The 3 secondaries received 200 connections.
The primary member received 1000 connections - the majority of which appeared to authenticate.. all of which remained connected over 20 minutes later.

The results from isMaster should be authoritative, not augmentative.