Yes, the gameplay IS NOT CANON. All the insane force powers that this guy has are gameplay only, only the story will count as canon. He is Vader's apprentice and therefore he is weaker then Vader, even if in gameplay he does things that Vader has never done. All gameplay in video games is considered N-canon (non canon) according to Lucasfilm. So therefore only the story will count, i.e. anything in cutscenes or the like.