Enabled HTML.Nofollow and set URI.Host but nofollow is add to internal links

I've found a relative question but it doesn't solve my problem.

http://htmlpurifier.org/phorum/read.php?2,5611

In my html page i have some links like:

<a href='http:\/\/mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='https:\/\/mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='http:\/\/sub.mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='https:\/\/sub.mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='http:\/\/www.mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='https:\/\/www.mydomain.com\/' target=\"_blank\">Link<\/a>

I set URI.Host like mydomain.com
$config->set('URI.Host', 'mydomain.com');

The results of HTML.Nofollow that i set
$config->set('HTML.Nofollow', true);
is:

<a href="http://mydomain.com">Link<\/a>
<a href="https://mydomain.com">Link<\/a>
<a href="http://sub.mydomain.com"  rel="nofollow">Link<\/a>
<a href="https://sub.mydomain.com"  rel="nofollow">Link<\/a>
<a href="http://www.mydomain.com"  rel="nofollow">Link<\/a>
<a href="https://www.mydomain.com"  rel="nofollow">Link<\/a>

Why are the other subdomain nofollow?

I try also whithout http and https. It works but i need them!
example

<a href='mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='sub.mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='sub.mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='www.mydomain.com\/' target=\"_blank\">Link<\/a>
<a href='www.mydomain.com\/' target=\"_blank\">Link<\/a>

<a href="http://mydomain.com">Link<\/a>
<a href="https://mydomain.com">Link<\/a>
<a href="http://sub.mydomain.com">Link<\/a>
<a href="https://sub.mydomain.com" >Link<\/a>
<a href="http://www.mydomain.com">Link<\/a>
<a href="https://www.mydomain.com">Link<\/a>

Start by reproducing the examples with URI.Host set to mydomain.com and HTML.Nofollow enabled, comparing bare hostnames with http and https URLs. Determine whether subdomains are intended to be treated as internal or external, then clarify or correct the behavior and verify it with a regression test if the project provides one.