This feature of Bulk Share when set, will only share the extreme child class of the table selected for sharing. For example, if the cmdb_ci_server is selected for sharing and this option is checked if the CI is actually a Linux server, only the cmdb_ci_linux_server record is sent.
When un-selected, the actual record of the targeted table is sent. So, for the above example, the cmdb_ci_server record is sent. Because it contains a sys_class_name value of the actual class, when subscribed to and reconstituted, it will produce all the necessary class hierarchy if the subscriber is a ServiceNow instance. However, if the subscriber is not a ServiceNow instance, you will only get one record.
When bulk sharing configuration items, selecting this option allows you to target a parent CI table but share all the child objects