mysqli_query throws warning despite using silenced error mode

[kamil-tekiela]

Description

The following code:

<?php

mysqli_report(MYSQLI_REPORT_OFF);
$mysqli = new mysqli('localhost', 'user', 'password', 'test');

$mysqli->query("SELECT (
        SELECT 1 AS val
        UNION ALL
        SELECT 2
    ) FROM dual");

Resulted in this output:

Warning: mysqli::query(): (21000/1242): Subquery returns more than 1 row in ...

But I expected this output instead:

PHP Version

PHP 8.0.20

Operating System

Windows and Ubuntu