Complete and utter bullshit.
You are referencing Arnold as an example of someone who TRAINED LIKE A BODYBUILDER to get big and strong, occasionally competed in powerlifting competitions (not his main focus), and with that in mind you decide to focus only on the powerlifts?
In order to get stronger in the bench, deadlift, and squat, you need to make the muscles involved bigger and stronger. How does that not register with you as "hypertrophy" training? What makes you think splitting up your body logically and training with a comprehensive list of exercises means you somehow won't be getting much much stronger?
What reasoning could there possibly be for focusing on developing these three lifts alone, when you aren't a powerlifter, and could logically get bigger and stronger by doing ALL the basic bodybuilding exercises?
Arnold Schwarzenegger (and every other successful golden-age bodybuilder) spent the same amount of time doing barbell curls and lateral raises, as they did doing bench presses and squats, because when you are a bodybuilder you aim for complete symmetrical development. Powerlifting is NOT the "daddy" of bodybuilding, and you absolutely do not need to reach some ARBITRARY level of performance in a COMPLETELY DIFFERENT SPORT in order to start bodybuilding with an intelligent program.
This bullshit is like saying you must learn to throw a football a certain distance before you can start training all-out for basketball. Are there similarities and valuable training tools common to each sport? Yes. That doesn't mean that one sport must DEPEND on the other.
One of the commonalities between powerlifting and bodybuilding is that yes, making a muscle stronger while giving it enough nutrients will make a bigger muscle, but beyond that these two sports are polar opposites in many ways.