The term "character generator" in video specifically refers to hardware that overlays text onto the video signal. That is, in this case it's not a "text mode",

The term "character generator" in video specifically refers to hardware that overlays text onto the video signal. That is, in this case it's not a "text mode", it's a bitmap graphics mode used for text, which appears likely just going by the screenshots. There weren't many computer systems taking this approach in 1978, since any bitmap mode would be RAM-hungry, so they were usually either text centric(Commodore PET) or had both text and graphics modes and hybrids(Apple II, Atari).