The Kolmogorov complexity is almost identical to the entropy (Kolmogorov complexity is applied to a given string, entropy applies to the thing producing it). The entropy estimates in the comic, if you prefer to think of it this way, assume a "wordlist attack" (they actually assume the most efficient attack possible, though in this case I guess you could say that's a "wordlist attack"). It's also assumed that the words are chosen randomly (from the comic: "four random common words"), not "off the top of my head," so no, human fallibility is not an issue with the scheme itself, so much as the way many people interpret the word "random," when in respect to entropy, it has a very specific meaning. It's therefore an undeniable fact that attacking those passwords would require trying an average of half the possible combinations, or 2^(entropy-1). These passwords are just as strong as fully random character strings, so long as you ascribe the correct entropy values.

If it helps, don't think of the words as words, but instead as random numbers. It just so happens that these random numbers are presented in a form that's easier to remember. And 4 random numbers between 0 and 2048 cannot be easily guessed.