As to the saying "practice something for over 10,000-hours and you will be at a world class level ."
Maybe...
But it seems to me that 10,000 hours of practice makes you a world class practitioner of your field.

Why not talk off your watch and feel what the master feels instead of the student.

Don Deleva painting, Huxleys Dream, Neo cubism and transcubism, Surrealist painting.
Huxley's Dream: Acrylic and composition leaf on panel, 6"x 12", 2017