Security management Users API does not show "externalRoles" for Crowd

SYMPTOM:

Unlike Web UI's Users page, Security management Users API does not provide same information for "externalRoles" for the Crowd users with the External role mapping.

Example 1:
The user detail for LDAP user "externaluser" shows "External roles" and "Granted" properly:

And API: /service/rest/v1/security/users?userId=externaluser shows externalRoles: "nx-admin":

[ {
  "userId" : "externaluser",
  "firstName" : "external",
  "lastName" : "user",
  "emailAddress" : "externaluser@standalone.localdomain",
  "source" : "LDAP",
  "status" : "active",
  "readOnly" : true,
  "roles" : [ ],
  "externalRoles" : [ "nx-admin" ]
} ]

Example 2:
The web UI for Crowd user: "test-crowd" shows expected external groups and granted:

But API: /service/rest/v1/security/users?userId=test-crowd does not show "externalRoles".

[ {
  "userId" : "test-crowd",
  "firstName" : "Test",
  "lastName" : "Crowd",
  "emailAddress" : "test-crowd@hajigle.com",
  "source" : "Crowd",
  "status" : "active",
  "readOnly" : false,
  "roles" : [ ],
  "externalRoles" : [ ]
} ]

Roles:

EXPECTED BEHAVIOUR:

Users API should show same information as web UI.

ACTUAL BEHAVIOUR:

The externalRoles for Crowd is not working.