Unable to manually delay Google Tag Manager

Hi there,

The situation is this one:

• I have set ‘Load JS Deferred’ to Deferred.
• I have set ‘JS Minify’ to OFF.
• I have set ‘JS Combine’ to OFF.
• I have entered googletagmanager.com in the JS Delayed Includes box.

The result is that the following inline JS code is not delayed.

function add_google_tag_manager() {
    ?>
    <!-- Google Tag Manager -->
	<script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
	new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
	j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
	'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
	})(window,document,'script','dataLayer','GTM-XXXXXXXX');</script>
	<!-- End Google Tag Manager -->
    <?php
}
add_action('wp_head', 'add_google_tag_manager');
function add_custom_script_after_body() {
    ?>
    <!-- Google Tag Manager (noscript) -->
	<noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-XXXXXXXX"
	height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>
	<!-- End Google Tag Manager (noscript) -->
    <?php
}
add_action('wp_body_open', 'add_custom_script_after_body');

What am I missing? How can I delay only Google Tag Manager?

Thank you.