Javed Sb in his explanation of verse no 4 of surah talaq says”The Qur’anic words are”wal laati lam yahzin”. In the Arabic language, the word “lam” is used for total and strong negation. Hence the expression cannot connote those girls who have not started to menstruate; it can only connote girls who have not menstruated in spite of reaching the age.”
I want to know how does this particle “lam” specify this cause.
First we need to understand what would be the difference between “wal laati lam yahzin” and “wal laati ma yahzin”. Both sentences can be loosely translated as “and the ones who do not menstruate” however in this rather generic use of words in the translation the difference between Lam and Ma is not incorporated. As you correctly quoted from Mr. Ghamidi, Lam in Arabic is for strong negation.
Now the question is, if the verse refers to those girls who have not yet started to menstruate then what was the reason for using Lam and what aspect of this negation was strong in any aspect. However, if we consider this to refer to those woman who because of their age are expected to get menstruation yet for some reason they do not get it, then a strong negation does have an application as it refers to an unexpected and rather unusual case.