World class bouldering w/out campus training?

In today's World Cup scene, is campus board training necessary to become a world-class boulderer? I know Adam Ondra won the Boulder WC, without campus training. But he is a mutant (I mean that in a positive way). Other top climbers I read about say they do campus train a lot. Can you train campus without getting injuries? Do you need campus boards, if you're not Adam Ondra, and hope to make WC finals on a regular basis? Or does climbing itself build your strength enough, so that campus training is not necessary? Thanks...