I'm also using 2.2.a3 on both my test and live sites. This feature does work and I tested again today. Have you clicked on "Save and Create .htaccess" to generate the new .htaccess file? If all worked, your .htaccess should have blocks like this one:
RewriteCond %{HTTP_HOST} ^www\.example\.org [NC]
RewriteRule (.*) http://www.example.com/$1 [R=301,L]
where the OLD domain name is mentioned in the first line and the NEW is mentioned in the second line. If you see that, this .htaccess Maker feature worked as expected.
Please note how this feature works. If your site is www.example.com and you put "www.example.net,www.example.org" in that setting, then www.example.net and www.example.org will be redirected
to www.example.com. However, example.net (without the www) and example.org (without the www) will not be redirected as they are different domain names. Yes, the subdomains do matter. In fact, each subdomain can be hosted on a different server. For instance cdn.akeebabackup.com points to an Amazon CloudFront distribution (various servers behind a multicast DNS), whereas www.akeebabackup.com points to our web server. Different subdomain = a completely different site. That's why there is no subdomain wildcard in the generated .htaccess.
Finally, it goes without saying that for this feature to work, all domain names must point to the exact same hosting account. This means that, in our example, all three of www.example.com, www.example.net, www.example.org should point to the same hosting account and the same Joomla! installation (the one where you are using Admin Tools) for this redirection to have any effect. Obviously, if the domains are on different servers / hosting accounts / web roots then there is no way this redirection can work.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!