This is required by hot-restart support in Search Envoy. (CLOUDP-175049) The implementation need to be backported to 6.0.
If a search/planShardedSearch command fails with a network error (i.e. connection closed before mongos/mongod receives a response), the command will be retried at least once.
The retry loop will be applied to all the search/planShardedSearch requests. No other protocol changes are required.