Never played with WP Unix that much, but the notion that their printer driver system could be adapted to terminal output doesn't seem surprising: it could print that image on dot matrix printers speaking several different "printer control language" variants, some of which required some ingenious hacks. Terminal graphics fit quite well within that family.

WP also had pretty good support for the early laser printers, which had a wide range of ways to tell them to do stuff. Some wanted bitmaps, some built their own and you had to sent them fonts; etc. It was UGLY.

IIRC they even had some drivers for optical type setter things, the old stuff that used thermal paper. Not sure of those made it to version 5 era.