Filter on comment_reply_link and missing arguments

Hello!

I want to place filter for comment_reply_link data flow. OK, setup it:
<?php add_filter('comment_reply_link', 'comment_reply_link_filter',99); ?>
Now, according to Plugin API/Filter Reference:

comment_reply_link … Filter function arguments: link (string), custom options (array), current comment (object), current post (object).

Indeed, in comment-template.php file we can see:

function get_comment_reply_link(...) {...
return apply_filters('comment_reply_link', $before . $link . $after, $args, $comment, $post);}

Four arguments sended to filter, as you see.
So, my hook comment_reply_link_filter can expect all these 4 arguments as it’s input:

function comment_reply_link_filter(){
$numargs = func_num_args();
echo "Number of arguments: $numargs<br />\n";
if ($numargs >= 1) {
         echo "1st argument is: " . htmlspecialchars(func_get_arg(0)) . "<br />\n";
     }
if ($numargs >= 2) {
         echo "2nd argument is: " . func_get_arg(1) . "<br />\n";
     }
if ($numargs >= 3) {
         echo "3th argument is: " . func_get_arg(2) . "<br />\n";
     }
if ($numargs >= 4) {
         echo "4th argument is: " . func_get_arg(4) . "<br />\n";
     }
} ?>

Output of my filter:

Number of arguments: 1
1st argument is: (correct_link_here)

How it can be at all?? Where is another 3 args??