They didn't really show him much in the SNES instruction booklet either...He got relegated to a background pic on the warranty info page...oh, and that one pic of Crono, Frog & Lucca fighting him prior to the "Adventure guide"...and on the last page before the warranty thing it shows the confrontation on the cape among the pics talking about the multi-ending aspects of the game...In the PSX one though, he's as prominent as the other characters, really...but we all know how lame that port was...I chalked that one up to yet another mistake of that whole fiasco...
But, yeah, Magus was really a fairly spoilerific optional character...To include him in such would sort of ruin the story...So I guess so does that Tech guide thing...but who really looks at those anyways?