PHP autoload function return values do not make any sense!

A.php

<?php class A {}

autoload.php

<?php

spl_autoload_register(function($class) {
    echo "autoloader 1\n";

    if ($class == 'A')
        include 'A.php';

    if ($class == 'C')
        return true;

    if ($class == 'D')
        return false;
});

spl_autoload_register(function($class) {
    echo "autoloader 2\n";

    if ($class == 'B')
        include 'B.php';

    return true;
});

spl_autoload_register(function($class) {
    echo "autoloader 3\n";

});

echo "instantiate A...\n";
$a = new A();
echo "instantiate B...\n";
$b = new B();
echo "instantiate C...\n";
if (class_exists('C'))
    echo "C exists\n";
echo "instantiate D...\n";
if (class_exists('D'))
    echo "D exists\n";

B.php

<?php class B {}

Output:

instantiate A...
autoloader 1
instantiate B...
autoloader 1
autoloader 2
instantiate C...
autoloader 1
autoloader 2
autoloader 3
instantiate D...
autoloader 1
autoloader 2
autoloader 3

PHP source says the same: https://github.com/php/php-src/blob/1d6a136051051e4e25f89a280ca92fde2da04463/ext/spl/php_spl.c#L411