It's not unlikely that "correcthorsebatterystaple" is in several password attack dictionaries now, so sites may be legitimately ranking it as a weak password.

It's not unlikely that "correcthorsebatterystaple" is in several password attack dictionaries now, so sites may be legitimately ranking it as a weak password. But more importantly password strength meters don't result in stronger passwords. I saw an analysis a couple of months ago (unfortunately I didn't save the link) where they found showing password strength to the user had no impact on the strength of the password used. People would pick a password and then stick with it regardless of strength advice.