He talks about exactly about pattern matching and mentions latex using it in the second section. Also that this approach doesn't work as well with German compound words which is the whole premise.
To be fair, in day-to-day use problems like these will be corner cases as to my knowledge LaTeX tries to avoid hyphenation and even if it has to split a word, it has a good chance of getting it right. Also, to me this project's focus was more on learning about neural networks than creating a better hyphenator.