SteveInWA, hello once again:
I did confirm the legacy GV settings - correct TZ there. Your comments got me thinking, so I popped onto Webmin to see how the Linux IP PBX box was set. I was surprised to discover that, in fact, it was set one hour ahead. I was unaware that the Obihai was getting NTP data from the PBX, but, as you say, you've seen it happen yourself. Good one! We've got a couple dozen Polycom units here and they don't behave that way. If I were in WA, I'd give you a pat on the back myself. This is definitely worth documenting somewhere.
As to GV, I think the strategy I will next assay is to let it sit for 24 hours with the GV SP deleted (to avoid continuous registration attempts) until the Google host timer resets. If I keep the current config and simply add GV as a penultimate step (need to set the line appearance, but otherwise no fiddling) I think that might do it. I considered the effect of high-frequency re-registration at GV earlier on in the process, but could find no documentation on that issue. It was weird that I got fails on all three GV accounts, but maybe they were blocking the subnet's public IP address.
With respect to the frequent restarts, for all the 500 and 600 series Polycom IP phones we've had, few of the config changes triggered restarts. A good thing, actually, since the Obi phones are WAY faster to reboot than the Polys. I mean...like five minutes for a restart. I see the same thing on the IP phone/cam equipment we have on doors and gates: make a bunch of changes and you get a message that says "RESTART THE DEVICE FOR THE CHANGES TO TAKE EFFECT"
Again, many thanks for the TZ hint! <sigh> now to get back to MUCH less fun stuff....