The deliberate part is so often overlooked since most people only know training with a teacher, where they give the responsibility for the deliberate part to the teacher without even knowing.

If you start learning by yourself from every 10 hours of practice maybe only 1-2 might count as deliberate. If that efficiency is tracked as well, one could argue that even a motivated learner might take up to 20k hours to get to his 10k hours of deliberate practice.