When making configurations changes, such as removing a secondary, it drops connections to the primary. Not sure if sharding affects this or not.

The feature request is no connections to the primary should be affected (other than replica connections) for any changes to the replica set where a majority of servers is up and the primary server stays the primary server.

From a systems administration point of view, when systems go down or need to be replaced in production live, the primary dropping all of its connections is very bad. The changes to the replica set should go unnoticed to the primary.