I am trying to add a custom_vars to my wordpress site using version 6.5.3 (Hebrew)

The template is Twenty Twenty, and I disabled all the plugins.

The problem is that after adding the query_vars, access the site with http://localhost?city=whatever returns the posts page.
Accessing the site normally without the query_vars (http://localhost) returns the statis page as expected.

This is the code that I added to wp-content/themes/twentytwenty/functions.php:

function myplugin_register_query_vars( $vars ) {
    $vars[] = 'city';
    return $vars;
}
add_filter( 'query_vars', 'myplugin_register_query_vars' );


function myplugin_rewrite_tag_rule() {
    add_rewrite_tag( '%city%', '([^&]+)' );
    add_rewrite_rule( '^city/([^/]*)/?', 'index.php?city=$matches[1]','top' );
    
}
add_action('init', 'myplugin_rewrite_tag_rule', 10, 0);

Any idea why?