Actually, an extra 10 days doesn't do that. The extra 10 days gives it a root system the size of your fist instead of a golf ball. That extra root mass is what gives it the edge.During that time, the plant matures, prepares for reproduction and reaches it 's full potential.
That's why, once a root system is established, vegging an extra 2 weeks does increase yield, but the huge difference between 4 days vegging and 10 days doesn't scale up the same way between 10 days and 2 weeks.
The 'maturation' should really be done before you even clip the cutting. All of my mums are over 5 months old and are fully mature, ready for flowering out.