User blog comment:KidVegeta/Canonicity/@comment-3097771-20101130082822/@comment-3097771-20101130084447

I disagree. At this time, Goku hadn't trained in Super Saiyan at all, and might have been hesitant to use it again (without knowing what could happen). It's one thing to transform, in show, but it's completely different to transform again, in the heat of battle, completely taken off guard. -KidVegeta