@jave-web , @roby94 is actually right. This was really annoying for me so I tracked it down.
wp-admin/includes/plugin.php on line 1328 (5.5.3)
$admin_page_hooks[ $menu_slug ] = sanitize_title( $menu_title );
current_filter will return the correct filter but the correct way is
sanitize_title( $parent['menu_title'] ) . '_page_' . $child['page_slug']
