You have to pick the words uniformly, yes. Thankfully, that's easy to do (rl -c 4 wordfile), and can be made easier. The point isn't "make up passwords that look like this" - it's "using this algorithm you get passwords that look like this that have this level of security[1]," and it's way easier than generating a secure and memorable password by other means.

[1] As I've said in a few places, the actual dictionary size and number of words should be tweaked to make the security level appropriate for your needs, which will vary by application and grow over time.