Chef Automate API - api

Question

Starting to use the Chef Automate API.
I'm new to using APIs and I am confused as to what they mean by "Authorization Action" as listed on the documentation site:
I am using Postman as my utility/tool, and I have a Chef Automate admin API key. When I do a query:
GET {{ChefAutomateURL}}/apis/iam/v2/users?id=userid3
I would assume the reply would be only for that single user, but instead i'm getting everyone returned:
{
"users": [
{
"name": "user1",
"id": "userid1",
"membership_id": "a745cc00-8521-42a6-97ca-a60ccef931"
},
{
"name": "user2",
"id": "userid2",
"membership_id": "22e8e761-443b-45a3-9bdf-6ab4ccf79a"
},
{
"name": "user3",
"id": "userid3",
"membership_id": "67d2e924-2424-44d0-854d-c303f6c5ec"
}
]
}
... and I'm really confused as to why this isn't working.
This extends into my real desire, which is creating a local admin user, but again, when I try to do that, the response is just a JSON body with everyone:
POST {{ChefAutomateURL}}/apis/iam/v2/users
with this raw body:
{
"id": "userid4",
"name": "user4",
"password": "str0ng_password!"
}
I get a 200(OK) response like:
{
"users": [
{
"name": "user1",
"id": "userid1",
"membership_id": "a745cc00-8521-42a6-97ca-a60ccef931"
},
{
"name": "user2",
"id": "userid2",
"membership_id": "22e8e761-443b-45a3-9bdf-6ab4ccf79a"
},
{
"name": "user3",
"id": "userid3",
"membership_id": "67d2e924-2424-44d0-854d-c303f6c5ec"
}
]
}
I assume it has something to do with the "Authorization Action" as that's the only thing I'm not explicitly sending, but I don't understand what that is, or where/how it fits into the query.
I appreciate the help, thank you!