Input required settings: text value / format is not saved

When using a "Input required" exposed form, setting a text in "Text on demand" and applying does not save the entered value nor format.
Using an exported view with :

  $handler->display->display_options['exposed_form']['options']['text_input_required'] = array(
    'value' => 'Please enter search terms.',
    'format' => 'plain_text',
  );

Does not work neither.