twentyseventeen_custom_header_args has no effect

Wanted to change the header size on frontpage.
Tried widely spread solution with no luck. Added filter to me child theme.

function my_custom_header_args( $args ) {
  $args['default-image'] = get_theme_file_uri( '/assets/images/header.jpg' );
  return $args;
}
add_filter( 'twentyseventeen_custom_header_args', 'my_custom_header_args' );

It had no effect on it. Used CSS solution from here https://wordpress.org/support/topic/home-page-menu-not-visible-with-safari-on-ipad/
at the end. Searched for better solution with no luck. Filters and actions just would not work.

Is that a problem of “2017” or am I making some common mistake?