After the user registration UI flow walkthrough, ZAP will be able to identify more URLs.

The active scan will be able to explore more security based on the newly identified URLs, as follows:

$ CURL "http://localhost:8090/JSON/ascan/action/scan/?zapapiformat=JSON&formMethod=GET&url=http://hackazon.webscantest.com&recurse=&inScopeOnly=&scanPolicyName=&method=&postData=&contextId="