Content selector privilege API requires "format"

The content select or privilege creation REST API requires format:

{
"name": "string",
"description": "string",
"actions": [
"READ"
],
"format": "string",
"repository": "string",
"contentSelector": "string"
}

I can see no way to leave it out, it results in an error saying format is required. However the content selector privilege UI does not even allow format to be specified. And additionally, you can create a privilege against "all repositories", where format clearly should not be required.

Expected: Format should be optional for the API, or remove entirely to be consistent with the UI.