... when considering all of them Pre-16 years, that is?
Hong and Ouyang continued to improve at partial 9 Yin rate, stated to be the main reason for their significant improvement. Huang and Yideng did not have this luxury, so would they have improved at a slower rate perhaps?
But then again, Zhou Botong was improving at partial 9 Yin rate all along, and though he got a head start at the beginning, he did not seem to improve any faster than the other Greats after a few years.