Not updating the value in the DB you’ll need to add some conditionals in your load field filter so that it is not altered when editing the field group.
add_filter('acf/load_field/name=field_name', 'alter_message');
function alter_message($field) {
$post = get_queried_object();
if (isset($post->post_type, $post->ID) && $post->post_type != 'acf-field-group') {
// alter the field
}
return $field;
}