Doing both of these together made mine stop prompting on Windows Pro, most recent update as of July 15th 2018:
- Click Start and search "Edit group policy"
- Go to Computer Configuration -> Administrative Templates -> System -> Logon
- Double click on "Turn on convenience PIN sign-in" and select "Disable", then "Ok
- Make sure on your sign-in page (on startup) that the icon for password (under the password box) is selected.
Personal Note: Whatever backwoods software dev thought that forcing this on and making a user use Group Policy, an advanced Windows settings area, to turn it off needs to be reigned in. Like many Microsoft things, the idea is cool, but the execution is terrible.
Of course that won't work on Windows Home -- only Professional.