Docs.

Author: johnbillion

src/wp-admin/includes/class-wp-site-health.php

@@ -941,6 +941,7 @@ public function get_test_php_extensions() {
 				'function' => 'mysqli_connect',
 				'required' => false,
 			),
+			// Sodium was introduced in PHP 7.2, but the extension may not be enabled.
 			'libsodium' => array(
 				'constant'            => 'SODIUM_LIBRARY_VERSION',
 				'required'            => false,

src/wp-includes/compat.php

@@ -273,7 +273,7 @@ function _mb_strlen( $str, $encoding = null ) {
 	return --$count;
 }
 
-// sodium_crypto_box() was introduced in PHP 7.2.
+// sodium_crypto_box() was introduced with Sodium in PHP 7.2, but the extension may not be enabled.
 if ( ! function_exists( 'sodium_crypto_box' ) ) {
 	require ABSPATH . WPINC . '/sodium_compat/autoload.php';
 }