I don't understand why the regulation 7 would specify from 18 years of age and upward - is FIFA attempting to thwart a worldwide football child prodigy smuggling ring to the Middle East?
Pretty much nail on the head.
So the way out of that (prevented from playing until 23) is you can request FIFA for a nationality transfer - as that's what the Australian example shows. But I still don't see where that situation is actually covered in the regs...it seems very unclear...because that part of the regs deals with the Winston Reid example where you have already played for another country