Update, something to try for everyone who's not getting it to work, found a bypass via the menus instead, you can forget using Tungkick's tool for the newest builds that have patched the hole.
Verified on US991 on 20a firmware.
From the first bootup screen, go to Accessibility, Motor and Cognition, turn on Touch Assistant.
Press on the icon that comes up, then press Home. In the Google search box that comes up enter settings, you'll see settings pop up, hit it, go to Apps. hit upper right three dots for menu, select Show System.
Disable every single Google app (Chrome, Slides, Sheets, Gmail, maps, Youtube, Hangouts etc. etc anything that is Google in origin.)
Disable all Google Play everything including Play Services and Store
Disable Google Account Manager and Google App
Disable Google services like calendar and contacts sync, text to speech I think, services framework, one time init, and partner setup
Also went to Security, Administrators, and removed Device Manager
---pretty sure I covered it...
back out of menu, reboot phone.
You should be able uncheck Wi-Fi and Mobile networks and still be able to hit Next at the bottom right, FRP check is disabled. Once it boots all the way into the interface, go to Settings, Backup and Reset and do a factory reset.
Done.