If one selects to sign into Windows 10 by typing a pin (instead of typing a password or using a fingerprint), NVDA announces the last number of the pin instead of replacing it with an asterisk (star). This happens regardless of whether or not the typed pin is correct.
This is with Windows 10 Pro 64-Bit, all recent Win 10 releases, and NVDA 2017.4, 2017.3, and 2017.2.
Quite interestingly, this doesn't affect the "Password" option.