"Lone coder" here. I reached out to Ollie (the FT reporter) because he'd written a book (Seven Games) about computers and games, so I thought the Boggle story might interest him. It did!
Nice work! I love an "impossible" problem that falls to bounding estimates like this one does. There was a surprisingly lot of work done in protein folding that had similar sorts of techniques to eliminate structures that would either never happen or would self destruct if they did kinds of things.