Add ACF fields to the content parser of Focus. See: https://github.com/sybrew/The-SEO-Framework-Extension-Manager/blob/2d70d5a141491209340b72a8cefeb574dd00b538/extensions/essentials/focus/trunk/inc/classes/admin.class.php#L99-L128

my-acf-focus-fields.php

<?php

// Ref: https://github.com/sybrew/The-SEO-Framework-Extension-Manager/blob/2d70d5a141491209340b72a8cefeb574dd00b538/extensions/essentials/focus/trunk/inc/classes/admin.class.php#L99-L128

/**
 * Adds my custom fields to the Focus parser.
 *
 * @param array $elements
 * @return array
 */
add_filter( 'the_seo_framework_focus_elements', function( $elements ) {
	$elements['pageContent'] += [
		".acf-field[data-name='my acf field name'] input"       => 'append',
		".acf-field[data-name='my other acf field name'] input" => 'append',
	];

	return $elements;
} );