Disconnecting 12 V Battery No Change to Customizable Options

I have been under the mistaken impression for some time now that disconnecting the 12V battery on a Gen3 Prius would reset the customizable options back to default settings. I had my battery unhooked for several hours today while working on an unrelated problem. When I reconnected the reverse beeper was still set to one beep and the extra seat belt beeps were still turned off, just as they were before.

The Nav addresses were still OK but the assumed speed settings needed to be reset. The clock also needed to be set. The trip mileages and the fuel mileage records were gone (there went my 73 MPG test drive). All of the Audio presets were gone. Didn't have BT set up so I don't know about that.

When I restarted the car it ran a bit weird (high idle speed) and had defaulted to Normal mode vice ECO. After 20 miles or so everything is OK again.