Is wp_reset_postdata() redundant after the main loop?

Question

I'm confused about an example from the docs:

<?php
    // The main query.
    if ( have_posts() ) : while ( have_posts() ) : the_post();
        the_title();                                                             
        the_content();                                                          
    endwhile;                                                                   
    else :                                                                      
        // When no posts are found, output this text.                           
        _e( 'Sorry, no posts matched your criteria.' );                         
    endif;                                                                       
    wp_reset_postdata();                                                        

    /*                                                                          
     * The secondary query. Note that you can use any category name here. In our example,
     * we use "example-category".                                               
     */                                                                        
    $secondary_query = new WP_Query( 'category_name=example-category' );        

    // The second loop. if ( $secondary_query->have_posts() ) 
    echo '<ul>';
    while ( $secondary_query->have_posts() ) :
        $secondary_query->the_post();
        echo '<li>' . get_the_title() . '</li>';
    endwhile;
    echo '</ul>';
    endif;
wp_reset_postdata();
?>

Isn't the first wp_reset_postdata() completely redundant? Before querying $post, the secondary query overwrites it anyways right? Is there ever a case where it makes sense to call wp_reset_postdata() after the main loop?

Answer 1

The first use of wp_reset_postdata() is not redundant its unnecessary.

Per the codex

Use this function to restore the global $post variable of the main query loop after a secondary query loop using new WP_Query. It restores the $post variable to the current post in the main query.

So only use it after your secondary query to reset things back for your main query.

NOTE: a better location to put it would be within the if instead of after the else

if ( $arg ) :
    // loop
    wp_reset_postdata();
else :
    // no results
endif;

More infor on wp_reset_postdata()