I've met a few post-docs from Germany in my time in grad school so far.
They are some of the most extremely independent scientists I've met. I say this as a grad student who is NOT a totally independent scientist yet. (I bug my adviser and the older grad students in my lab quite regularly.)
We have focused mostly on whether the immersion of grad school is overkill, but perhaps we should focus more on it's purpose.
There is something that happens to the way one thinks when you immerse yourself like one does in grad school. If you spend 60+ hours a week thinking about one topic, your brain becomes built to think about that thing. Your thinking process changes, permanently.
I'm noticing this happening to me now. I see the results in the older grads in my lab and in my adviser. For example, my adviser, the 6th year student, and the post-doc in my lab are all trained to think about science, all the time. They end up coming up with ideas that I find brilliant, to say the least. They are small things, like neat ways to align optics, and big things, like novel measurements we could run and then publish. They are all ideas that I would never have thought of, at my current stage of education anyway. Slowly, I notice myself having neat, new ideas the more I immerse myself in the field.
Everyone else in my lab has already thought of most of my ideas

, but still, the point is that this immersion trains you to be a successful scientist. Without these novel ideas, my adviser wouldn't get grants, the grad students wouldn't publish, and science would not get done.
And my personal experience tells me that this 60+ hour/week immersion is how you teach your brain to start thinking in this essential way.
So, before we go onto a tangent asking if the grad school work load is some strange, cultic, hazing ritual, let's ask if maybe there is method to the madness. Maybe there is a reason the system exists the way it does? Perhaps the intense immersion has an educational effect? I wonder what the other grad students and PhDs in this thread think about this point?