I thought bro STP made it quite clear about getting married at a young age or after reaching the age of puberty though he never mentioned any number like 9-14, anyway, in Islam getting married at an early age is only an option and not a religious law and it cannot be done without girl's permission.
I think both non-muslims and muslims girls reach puberty at 9-13, whatever he was trying to say, he was advocating 'child marriage' by saying he personally believes they should be married when they reach puberty.