Regarding document - How Does One Create Users and assign Roles without the IT_Security_Manager Role
This documentation of Oracle doesn't really address the actual how to question. The simplest answer to this question should be, it cannot be done without IT Security Manager Role. As you know this role provides additional capabilities other than just user management and role assignment, the actual business need could be to see whether we can have this user management and role assignment part alone be delegated to a named resource in the company. So the actual ask here is that: Oracle should consider creating a role that will provide access only to user management