The account should be disabled if the user has exceeded the maximum number of attempts. When the password expires or the account is locked SQL Server should disable the account. There is really no way to determine if the account has been disabled by exceeding maximum attempts or expiration. (Unless there is an error logged in the error logs besides failed login, but I am unsure of this)

SQL looks at the policy of active directory or local server depending on your setup. Another possible cause is your are looking a the local policy instead of the AD policy. You may want to examine the local policy to make sure it is correct, if you are using it. You can find it under Start | All Programs | Administrative Tools | Local Security Policy