Nobody was directly accessed to the forum, everyone was required to use a password.
I tested it myself, logging onto my non-admin board account. Once I had typed the password I could access the forum repeatedly until I actually manually logged my account out. I had to test it using the new password though, since I had never accessed the forum with the old password.
The person making the complaint to me was a moderator to the forum; would he be able to access the forum while still logged in on the old password? Possibly he exaggerated the situation to me when describing it, and it was only him who could still access without updating the password...