Freak of nature. I think both he and Spencer are also several years younger than Mark Hall was when he won his NC as a true freshman.
I would hate for facts to get in the way of your opinion
Mark Hall born January 11th, 1997, he was 20 years, 2 months, 8 days old when he won his title
Spencer Lee was born October 14th, 1998, he was 19 years, 5 months and 14 days old when he won his title.
Yanni Diakomalis was born Aprill 11, 1999 he was 18 years, 11 months and 7 days old when he won his title
Thus Hall and Lee are within nine months of each other, not several years as you want to claim. Yanni and Hall are one year and 3 months apart, again, not several years as you want to claim.
To compare
Cael Sanderson was 19 years, 9 months, 1 day old when he won his first title.
Logan Steiber was 21 years, 1 month and 23 days old when he won his first title
Kyle Dake was 19 years 24 days old when he won this first title