Source

File: wp-admin/includes/class-wp-site-health-auto-updates.php

public function test_wp_automatic_updates_disabled() {
		if ( ! class_exists( 'WP_Automatic_Updater' ) ) {
			require_once ABSPATH . 'wp-admin/includes/class-wp-automatic-updater.php';
		}

		$auto_updates = new WP_Automatic_Updater();

		if ( ! $auto_updates->is_disabled() ) {
			return false;
		}

		return array(
			'description' => __( 'All automatic updates are disabled.' ),
			'severity'    => 'fail',
		);
	}