вон почти сразу допер что не в docs надо было глядеть а в sheets )
$client = new \Google_Client();
$client->setApplicationName('Google Sheets');
$client->setScopes([\Google_Service_Sheets::SPREADSHEETS]);
$client->setAccessType('offline');
$client->setAuthConfig(DIR.'/../../../config/php-spreadsheet -985d9fb32d2c.json');
$service = new \Google_Service_Sheets($client);
$spreadsheetId = $this->modx->getConfig('g_sheet_id');
$sheets = $this->getSheetsNames();
$rows = [];
foreach ($sheets as $sheet) {
$response = $service->spreadsheets_values->get($spreadsheetId,$sheet);
$values = $response->getValues();
}