If you’re a young student intent on one day becoming a doctor, your future livelihood depending on your ability to become an expert in practicing medicine, then the incentives push you to over practice.
Like if someone, especially someone in a position of authority in the field, suggests a particular method of improvement, you’ll think, “What’s the harm? I might as well try it. I might as well put in 110% because (and this is key) I will do everything I can in order to insure that I master the field of medicine.”
In contrast, someone who hasn’t made that decision to do “whatever it takes” might be in a better position to improve faster. This person has to triage to decide what works best and do just that, instead of doing everything. And that strategy might help them learn more efficiently than others who go with “whatever it takes.”
Perhaps it doesn’t take 10,000 hours to get good at something. Perhaps people who want to get good at something just love it so much and bet so much on their success in that specialized field that they’ll put in 10,000 hours to insure they’ve tried every single approach possible to reach their goal, even if that’s not the most efficient way to reach it.