Hmm, they aren't clear whether it's fully voice-acted or whether he provided phonetic sounds for them to synthesize according to the text, but in either case, it's not AI whatsoever.

Important to note that ESS Technologies (the company cited there) was literally a company who made synthesized speech for video games.

Electronic Speech Systems produced synthetic speech for, among other things, home computer systems like the Commodore 64. Within the hardware limitations of that time, ESS used Mozer's technology, in software, to produce realistic-sounding voices that often became the boilerplate for the respective games.