You may be able to use the field parent and check for the group, but I’m not sure
I would also use prepare_field, not load_field
function my_acf_load_field( $field ) {
if ($field['parent'] == 'group_XXXXXXXXX') {
$field['disabled'] = 1;
}
return $field;
}
add_action('acf/prepare_field', 'my_acf_load_field');