That must be an amazing feeling! Is this a feature that's still in macOS today? Can I see it in action?
(which is random, but you need two columns in the PDF). Try select from column 1 near the bottom, across to column 2.
PDFs are very diverse. Our algorithm does not always work, alas, but it is significantly better than what existed before.
In fact, for some reason, it works well for this document on page 1 and 3 but not so well on page 2! But I no longer have access to the low level tools I used to use to figure out what went wrong.
PDFs are more "baked" layouts rather than high level semantic markup, so it's not easy to automatically determine this. The AI is probably a set of heuristics.