Suspicious code in align.el

[Artur Malabarba <bruce.connor.am@gmail.com>]

In line 890 of this file, there's a call to align-regexp that looks like this:

(align-region beg end
              (or exclude-rules
                  align-mode-exclude-rules-list
                  align-exclude-rules-list)
              nil
              separator
              (function
               (lambda (b e mode)
                 (when (and mode (listp mode))
                   (setq sec-first (min sec-first b)
                         sec-last  (max sec-last e))))))

Note how the separator here is passed as 5th argument, while the
docstring of `align-region' documents it as the 3th arg. Furthermore,
the exclude-rules are passed as 3rd arg, but they're documented as
5th.
Is this correct?

Apparently this was written 15 years ago, so this means I'm either
missing something or this code branch is never reached.

Cheers,
Artur