Quote - So what, is this a bug or is that just the way it is?

Yes, that's just the way it is, unfortunately.  

Quote - Incidentally, it seems to me we used to be able to expand the Object Parent window like we can the hierarchy window, but we can't now. Unless I'm just imagining that, which is entirely possible. ;-)

You mean resize the window? You can't do that in P6, though there might be a setting in the poser.ini file to set the size of that window.