My observation, I did not see anyone say anywhere:

It is noted by others, the puzzle author cites BIP-39, and then gives an example seed phrase with Electrum old wordlist. I myself think this is no accident. It must be a clue.

The author seems well-informed. Expert. I think they are playing dumb, not making a mistake. But what do they try to say with the discrepancy?

I guess it signals they did not use whatever wordlists others will use to try to solve it. All your CPU/GPU cycles are a waste. Seven years, almost eight years of money sitting there with an unsolved puzzle! It says all approaches are wrong.

In a puzzle designed as an essay about hiding information in text, I predict the only way to solve it is to get inside the head of the author. Read it as they read it. The puzzle was made to be intractable to computing power.

If Trithemius wrote an essay to hide a real wallet backup, what self-reminders may be needed? If Trithemius read the BIP-39 reference followed by Electrum phrase, what memory would it jog? It is by asking such questions, I reach my above conclusions.