To assist in the autoregistration process for agents, and to streamline onboarding of new hosts, the "Add host" action for Autoregistration should utilise the same "Hostname, Visible Name and Unique" criteria options as discovery.
While discovery is mechanically different, most of the time the end result is the same; add the host to Zabbix. To be able to specify the IP address as the unique criteria and/or hostname value, it allows Autoregistration to more closely align with how discovery works.
The way I see it, Discovery is a pull, and Autoregistration is a push. Other than the direction, they should behave the same, or similarly.