Shafique can't address the passages I've posted in the Koran confirming that husbands may have s.exual relations with prepubescent wives.
Waiting (Iddah) is only required if the husband has s.exual contact with his wife (v 33:49) yet we see in v 65:4 that prepubescent wives must also wait a period of three months before they can marry again:
Koran 33:49 - O ye who believe! when you marry believing women and then divorce them before you have touched them, then you have no right to reckon the period of waiting with regard to them. So make some provision for them and send them away in a handsome manner.
Koran 65:4 - And if you are in doubt as to the prescribed period for such of your women as have despaired of monthly courses, then know that the prescribed period for them is three months, and also for such as do not have their monthly courses yet. And as for those who are with child, their period shall be until they are delivered of their burden. And whoso fears ALLAH, HE will provide facilities for him in his affair.
A waiting period (iddah) is required for wives who have not yet menstruated. But waiting periods are only required for wives if they have s.exual contact with their husbands.
Therefore, the Koran not only legislates prepubescent marriage but also assumes husbands will have s.ex with their prepubescent wives.