The ability to reset a password from the login window X days from expiration has been around for a while if you're an AD mobile user with a GPO, or if you're a local account with an expiration policy.
/usr/bin/defaults write /Library/Preferences/com.apple.loginwindow PasswordExpirationDays $NumberOfDaysHere
There was a bug in 10.14 and 10.14.1 where if a user was updating to Mojave from an earlier version of macOS and was X days from a password expiration it would lock up or freeze during installation. So that release note is more of a bug fix so there's no failed install during the pw expiration warning timeframe.
