Woww
What I just tested shows that the any additional '9' or '999999' in the end of the passphrase gives the same address as the original passphrase. But different addresses were returned if '9' or '9999' was inserted in the middle of the original passphrase.
That's correct behavior.
So 'qwert999999999999999999' was thought to be more than 20 characters, but it is just 'qwert' 5 characters. I think the average people should know that.