Mentally autocorrected the title to "paypal cipher" and got enticed to click...

More seriously, this looks like the context modeling that advanced compression algorithms do, but in reverse.

Recovering the key does not settle the text.

That said, the Claudish in this article is only slightly annoying.

I had a sense. Pangram identifies this as AI.

I knew it was going to be cryptography. Everybody's cracking something these days. See also: https://news.ycombinator.com/item?id=49738551

Love this analysis!