What is an example of a "high-end page-layout program" referenced in that document? I mean, of course I assume they exist for professional type setting, book publishing and such, but I have never seen or heard of the actual software.

Thanks for that link! There is a bit more ... justification (pun intended) on that page for this recommendation to turn-on hypenation; and also some valuable advice on choosing spacing between words over spacing between letters.