Exception::$message can't be extends with string type

Description

Documentation book

The PHP book describes Exception class as follows:
https://www.php.net/manual/en/class.exception.php

class Exception implements Throwable {
/* Properties */
protected string $message= "";

[...]
}

Extending it:

https://3v4l.org/QtEA0#v8.2.1

<?php
class AException extends \Exception
{
    protected $message = 'New Default Message';
}

class BException extends \Exception
{
    protected string $message = 'New Default Message';
}

Resulted in this output:

Fatal error: Type of BException::$message must not be defined (as in class Exception)

But I expected this output instead:
No error. Or an error for class A, not class B.

PHP Version

PHP 8.2.1

Operating System

Start with the Exception class page linked in the issue and reproduce the PHP 8.2.1 examples to confirm the documented property type and inheritance behavior. Done means the documentation accurately explains the behavior and the examples no longer contradict the observed result.