Hi Brian:
I'm the guy (Bluescat) who wrote that reply over on the GV forum, about it simply being a bug.
I've done some more testing today, and it appears to have nothing to do with the Obi; I unplugged my Obi completely, then logged into GV, and confirmed that the "require a PIN" setting was selected for Google Chat, then I logged into GMail and dialed my GV number using the GMail Voice and Video browser plugin (AKA Google Chat). Sure enough, it does NOT ask for my PIN. This is a Google Voice bug, and as we GV users have found, you can just forget about them fixing anything like this.
If anyone cares to prove me wrong, I'd be delighted. I'll update my post over on the GV forum.