datagridValues prop is deprecated, another approach is https://docs.sonata-project.org/projects/SonataAdminBundle/en/4.x/reference/action_list/#customizing-the-sort-order

protected function configureDefaultSortValues(array &$sortValues): void
{
    // display the first page (default = 1)
    $sortValues[DatagridInterface::PAGE] = 1;

    // reverse order (default = 'ASC')
    $sortValues[DatagridInterface::SORT_ORDER] = 'DESC';

    // name of the ordered field (default = the model's id field, if any)
    $sortValues[DatagridInterface::SORT_BY] = 'updatedAt';
}