True, but there are broken ciphers that are resistant to a cryptanalytic version of this, which suggests that Pearl isn't covering all the ways to find regularity in data.

Indeed. I haven't finished Pearl yet, but from what I've read so far, it doesn't look like his models can handle iteration, vector-typed variables, model priors other than one particular interpretation of Occam's razor, or hidden variables more complicated than a two-variable correlation. So there's a lot of theory left to build, and cryptanalysis may have some lessons for that theory.