Hmm this is somewhat new behaviour, as this is really "array of type", the valid values being the enums. We might be better of using the jsonSchema way of doing this, rather than inventing our own.

Oh. I think I introduced this because roles ended up with an enum in my merge conflict:

'roles'           => array(
    'description' => __( 'Roles assigned to the resource.' ),
    'type'        => 'array',
    'context'     => array( 'edit' ),
    'enum'        => array_keys( $wp_roles->role_objects ),
),

I'll revert for now.

9fc8248