In the case where network isn't up, or a reverse lookup is not possible, the hostname box is blank. In the case where a reverse lookup is possible, only the domain part of the fqdn is filled in (ie ".click-network.com") I'm told that this is wrong, and should be fixed. While fixing, many of us find it odd that the screen talks about a hostname everywhere, but then expects a fqdn filled in. Perhaps this mismatch can be corrected (yeah, sorry about the pile-on) Putting it on the blocker tracker.
If network isn't up, the box is getting populated with 'localhost.localdomain', which is correct. I can't get an empty box to show up anymore. Likewise, when I do have network up for, say, stage 1, I get the FQDN in the box. The screen doesn't require an FQDN, but will accept it. By default, I try to populate the box with an FQDN if I can. If I can't, I just put the value of Hostname from NetworkManager. If that's nothing, I try a few other methods until finally falling back on 'localhost.localdomain'. At any rate, not seeing the problem in the latest rawhide that I have.