Went back to the other code you suggest:
add_filter('acf/options_page/settings', 'os_acf_options_page_settings');
function os_acf_options_page_settings( $settings ) {
$settings['title'] = 'Theme Options';
$settings['pages'] = array('Header', 'Sidebar', 'Footer');
return $settings;
}
and it works fine, but using the previous code posted with title and slugs still not working.