That this conclusion is not “mine” out of some sort of malevolent lie-spreading, here is a few tafsirs from two major Islamic scholars:
And then Tafsir Al-Tabari (9th Century):
The interpretation of the verse “And those of your women as have passed the age of monthly courses, for them the ‘Iddah (prescribed period), if you have doubt (about their periods), is three months; and for those who have no courses [(i.e. they are still immature) their ‘Iddah (prescribed period) is three months likewise”. He said: The same applies to the ‘idaah for girls who do not menstruate because they are too young, if their husbands divorce them after consummating the marriage with them.
And from the twentieth century which is clearest of all, the tafsir from Abul Mawdudi(20th Century):
They may not have menstruated as yet either because of young age, or delayed menstrual discharge as it happens in the case of some women, or because of no discharge at aII throughout life which, though rare, may also be the case. In any case, the waiting-period of such a woman is the same as of the woman, who has stopped menstruation, that is three months from the time divorce was pronounced.
Here, one should bear in mind the fact that according to the explanations given in the Qur’an the question of the waiting period arises in respect of the women with whom marriage may have been consummated, for there is no waiting-period in case divorce is pronounced before the consumation of marriage. (Al-Ahzab: 49). Therefore, making mention of the waiting-period for the girls who have not yet menstruated, clearly proves that it is not only permissible to give away the girl in marriage at this age but it is also permissible for the husband to consummate marriage with her. Now, obviously no Muslim has the right to forbid a thing which the Qur’an has held as permissible.
The girl who is divorced in the state when she has not yet menstruated and then she starts having the menses during the waiting-period, will reckon her waiting-period from the same mentruation and her waiting-period will be reckoned just like the woman who menstruates regularly
The article I took this from is here: