There's also something in the PHEV section of the owner's manual about "It may take up to 20 seconds to open the fuel filler door" after you push the button on the dashboard to open the door. Apparently there's some sort of depressurization that happens and can take up to 20 seconds. I'm wondering if the "valve" that closes after 20 minutes might be there for some sort of pressurization logic, but I don't really get why this would be specific to the PHEV. Also, isn't the max voltage on the PHEV and the HEV traction battery the same? I thought the difference was just about how much capacity (kWh) that can be restored in the respective batteries. If the voltage is the same, then the spark potential is the same, so the logic should be the same.
On a related note, has anyone else had difficulties with refueling? When I stick the hose nozzle all the way in the tank and try to run the gas pump, the pump kicks out after a few seconds in the same way that it would if the tank was full (but the tank is nowhere near full). I usually have to reposition the nozzle one or two times to find the sweet spot that will let fuel flow into the tank without prematurely kicking out. I went through this a couple of weeks ago and apparently I left the nozzle backed out a bit too far when I repositioned it the third time: the tank filled to overflowing and pumped out about a quart of gasoline onto the pavement before I could react and shut it off (good thing I hadn't walked away). I notified the attendant of the fuel spill, and they came out and cordoned off the filling spot until they could clean it up, but this is starting to feel like a real concern, rather than just a minor annoyance.