I wanted to show post by category using customizer. I was able show and select category using customizer. But all posts are showing not by categories

Question

    //  adding category select to the customizer

        //Get an array with the category list
        $silicon_cac_full_list = get_categories(array( 'orderby' => 'name', ));
        
        //Create an empty array
        $silicon_cac_list = [];

        //Loop through the array and add the correct values every time
        foreach( $silicon_cac_full_list as $silicon_single_cat ) {
            $silicon_cac_list[$silicon_single_cat->slug] = esc_html__( $silicon_single_cat->name, 'silicon' );
        }
    
    $wp_customize-> add_section('silicon_category_post_sec', array(
        'title'                    => __('Category','silicon'),
        'description' => __('Category you select here will be displayed in featured area','silicon')
     ));
    

     $wp_customize-> add_setting('silicon_category_post_set', array(
        'type'       => 'theme_mod',
        'capability' => 'edit_theme_options',
        'default' => 'uncategorized',
     ));

     $wp_customize-> add_control( 'silicon_category_post_ctrl', array(
        'label'                   => __('Category','silicon'),
        'description'             => __('Category you select here will be displayed in featured area','silicon'),
        'section'                 => 'silicon_featured_post_sec',
        'settings'                => 'silicon_featured_post_set',
        'type'                    => 'select',
        'choices' => $silicon_cac_list, 
    ));
    

I wanted to show posts by the category I selected in the customizer. But the problem is it is showing all posts. Even after selecting any category.