Is one exercise per muscle group enough for hypertrophy if done correctly?

YES! One and done. This is what the current scientific literature shows. One set per body part, 8–12 repetitions, each one performed in good form to absolute total momentary muscular failure (Until you cannot perform another repetition in good form no matter how hard you try). Only by doing this are you creating sufficient stimulus for maximum growth. It is not the AMOUNT of exercise that you are performing; it is how HARD you are performing it. If you are working out as hard as you possibly can, there is no way that you can continue a long drawn-out workout. A full body workout should only take 30 minutes MAXIMUM. This workout is performed three times weekly on nonconsecutive days. When you can perform more than 12 repetitions on any exercise in good form, increase the resistance by 5% next workout.