A shardCollection(nss) request  creates nss when this does not exist yet; nevertheless, such a creation may be undone on a later stage in case the request cannot be committed (e.g. as a consequence of a parallel addShardToZone committing a new unsatisfiable constraint).

When this happens,  the coordinator of shardCollection issues a dropCollection command for the newly created collection on each local catalog to ensure the proper rollback of the request.

Such a step is nevertheless incorrectly marked  on the primary shard as fromMigrate:: true, which prevents open change stream readers for nss from correctly tracking the drop of the collection.