From what I remember of the comic, the point was not the length of the password. The entropy was calculated based on 4 possible words.

Assuming ~2000 common English words, the number of possible passwords in that format is 2000^4 ~= 2^44. If the calculation is based on a completely random string of letters it is far stronger at 26^30 ~= 2^141 but it's safe to assume people aren't going to memorize a 30 character random password.

It's worth noting that the fairly common 8 character upper/lower case, numbers, and symbols they cracked in 6 hours is more secure than "correcthorsebatterystaple" at 72^8 ~= 2^49.