Xue Sheng
All weight is underside
My first shifu (from . Some of his students started calling him master. He did not look at all comfortable with the title. Then one day he asked them to stop, and told them there are mo masters under 60. He was in his 50s at the time and started training when he was 5.I think just looking at the years is a bit misleading. If you look at the hours involved, undergraduate study generally amounts to at least a half-time job, while doctoral study is equivalent to a full-time job. Meanwhile the average hobbyist martial artist trains probably 2-6 hours per week.
I'll assume that the sort of person who reaches 4th dan in TKD is more dedicated than the average student, so let's say they average 6-8 hours per week with no time off. That comes out to 3640 hours over 10 years. Certainly respectable.
In comparison, let's look at someone who completes a bachelors degree in 4 years and then a PhD in another 6 years (which is the average in the U.S.. Allowing for summer vacation during undergraduate study, that comes out to about 13260 hours. Significantly more.
To be sure, there are martial artists who train full-time. Someone who trains 20-40 hours per week for 10 years is likely to have really impressive levels of skill and knowledge. (Assuming it's quality training and not just going through the motions.) But these individuals are definitely the exception.
None of this intended to pick on you or on TKD. I see people in the BJJ community doing the same thing equating the years to get a BJJ black belt with the years to get a PhD, ignoring the fact that most BJJ black belts are not full-time professionals.