No Need to Use "add_theme_support('menus') According to WordPress Reference

In the video, Zac said we need to enable menu option in admin dashboard by adding this line in our functions.php:

<?php add_theme_support('menus'); ?>

However, we probably don't need that line, according to the function reference for register_nav_menus($locations):

"This function automatically registers custom menu support for the theme, therefore you do not need to call add_theme_support( 'menus' );"

And here is the weird thing:

I commented out the add_theme_support('menus') line, and the menu option seems to still work. However I then commented out everything about menus in functions.php, but the menu option in admin dashboard still seems to work. Here is the code I commented out:

<?php
add_theme_support( 'menus' );

function register_theme_menus () {
    register_nav_menus( [
        'primary-menu' => _( 'Primary Menu' )
    ] );
}

add_action( 'init', 'register_theme_menus' );
?>

That's a bit weird. Can anyone explain what happened? My best guess is that when we tell WordPress to enable theme support for menus, it remembers it somewhere in database, so deleting the code later on won't remove the support, since we didn't touch the database. If I really want to remove any feature, I can do

<?php remove_theme_support( 'menu' ); ?>