On the documentatio page - https://www.zabbix.com/documentation/current/manual/discovery/auto_registration the use cases and the behavior of the HostInterface and HostInterfaceItem is not detailed enough as it stands.

For example, the fact that using an IP address in the HostInterface parameter will populate the IP Address field and change the connect to value to "IP" needs to be emphasized, ideally with an example use case.