It actually will as long as they are RANDOM words. The random is the hard part. Humans are actually very bad at coming up with random values. If you ask people to pick a random number between one and ten a significant portion (usually 20% to 50%) will randomly pick seven and very few will pick one or ten.
Apart from the "random" issue, there is one more problem.
The site quoted is using a list of 7776 English words, but if you ask me to pick a few words myself, I would probably be picking the words from just a few hundred words (probably items in my house, people's name, brand name etc.).
BTW, how is the entropy of the password calculated?