Aha! I was fooled by that at first as well!
You'll notice that it only presents mysql hostnames in the drop down box for "Use existing hostname".
At this point, it's probably obvious to you what is going on, but that section specifies the MySQL hostname that your phpBB installation is going to use. If you search around here on the forums, you'll find several opinions on whether to create a new MySQL hostname for every one of your sites or to use a single MySQL hostname for each of your sites.
The bottom line is to do what you want. I create a new hostname for each domain, but not for each subdomain. This eliminates any cross-domain dependencies in my setup so I can drop or move a domain to another host (no, no Michael, I'm not actually thinking of doing this, I'm just using this as an illustration for
who's at the door?
no one's home! go away!
Free unique IP and $67 off with code [color=#CC0000]LMIP67[/color] or use [color=#CC0000]LM97[/color] for $97 off. Click for more promo code discounts