My Pixel C tablet doesn't respond to the unlock pattern and the recommend action to debrick it doesn't work
Just in case anyone else comes this way searching for an answer, I did get one on the XDA forums.
The solution is to start the device with volume down and power pressed.  This brings you to the menu I described in my original post.
Select the Reboot in Android recovery option.  Once you get the dead android logo hold power then press and release volume up, then release power.
That will bring up another menu which allows you to do a factory reset.
Once that is done you can restore your tablet.