The login form of course used the entirety of the password, not truncating it. Fun stuff.
It also doesn't sanitise or warn about the password having impermissible characters that will mess up the user's account the SQL Server that backs GP. Then, after an admin tries to reset the user's password (typic'ly to something like "Password1!"), the user can log in with the insecure 'temporary' password as many times as they want, but cannot change to a new password. When the user tries, GP claims success and says to use the new password at next login…but when logging out announces that the password failed to change.
I found out I could just enter the first 20 characters and log in. I've had other websites that simply broke. The worst one had a password reset page that also didn't verify their own password length limits, sending me in a frustrating password change loop.