That is correct BUT there are a couple of things I would say about it (I'm no expert, these are just my observations of things you might want to consider):
- Some people would argue against integrating your forum into Joomla because you then have to load Joomla AND phpBB3 on the same page which may slow down your page loads etc.
- You'll probably still want to modify your phpBB3 template a bit to match the rest of your website properly anyway
- Depending on how much work is put into the Artio plugin you may not have as much control over your URLs as you get with phpBB3 SEO
- They've probably fixed it with the recent releases, but I was finding when I used JFusion in integrated mode that certain operations and images didn't work as expected in phpBB3, which was another reason why I finally decided on the Direct Link mode
As far as duplicating your Joomla template goes, I see your point - I used ja_purity for my Joomla site and found a phpBB3 template based on this. I then used trial and error and a little research to get exactly what I wanted (I'm not a programmer or web designer so I don't know PHP etc.).
If you have a custom Joomla template then finding a suitable ready-made phpBB3 template will of course be harder.
Hope this gives helpful food for thought - in my opinion an Artio pllugin for JFusion with integrated phpBB3 would be a very helpful option if properly developed, but I don't see this setup being a magic bullet.