He was not a cryptographic savant. His first codes were broken in a week, his latter stood up to scrutiny because they had encoding errors, so any attempt to decrypt using the intended method would fail.

They thought they were the smartest person, so they tried to show off by publishing ‘clues’. All they did was show the world they can’t spell.

And the misspelling of words also adds an unintended layer of difficulty to solving the cypher.

In relation to the notes taking effort away from boots on the ground, I don’t think so. The beat cops don’t go down to the lab and do blood work themselves, so I doubt they went to the crypto lab to decode messages.