RecursiveRegexIterator insufficiently documented

Description

For example, __DIR__ contain symfony/console.

<?php
$iterator = new RecursiveRegexIterator(
    new RecursiveDirectoryIterator( __DIR__, RecursiveDirectoryIterator::UNIX_PATHS),
    '/((?:[A-Z][a-zA-Z\d]+\/)*[A-Z][a-zA-Z\d]+)\.php$/',
    RegexIterator::GET_MATCH,
    RegexIterator::USE_KEY
);

Resulted in this output :
Matches all class files in directory and sub-directories

But I expected this output instead:
Matches all class files only in root directory

PHP Version

tested only in PHP 7.3

Operating System

No response

Start by reading the RecursiveRegexIterator documentation and the supplied RecursiveDirectoryIterator example. Determine how recursion and the regex options should be explained, then update the relevant documentation so the iterator's matching scope and expected output are clear.