This particular function is easy to reverse though. Using appropriate data structures you can start with the end result and find all possible candidates for the word in polynomial time.
Bob can always just fall back on rubber hose cryptography.
I doubt writing a crossword solver is an easier solution since that would need to deal with word definitions and is hence a natural language problem.
I see crosswords as a data problem: given a dictionary of valid words, generate all possible solutions for the given grid. As the number of overlapping words is quite limited, shouldn't take long to run. The only natural-language factor is deciding which solution matches the clues provided. Dang, now I'm gonna have to go write one...
This is an example to show people what a one way function looks like. I even say at the bottom of the blog post that you wouldn't do this on a computer. This specific one way function is hard for a human to reverse. Writing a computer program to automate Bob's work is completely missing the point.