So when he wishes to exclude, he is actually excluding the exclusionaries.
Let me explain.
There are those who explain the raison d'etre of Pakistan through religion. That is how the Muhajir, according to him, claim a proprietary right to Pakistan; that is why Urdu was imposed on the new state, rather than Persian (remember that their national anthem is in Persian). So he is particular about excluding Muhajir, unless they accept that they are an additional element in the Indus-centric Pakistan.
There are those who explain the raison d'etre of Pakistan by denying their entire pre-Islamic history. That is how the racists, who claim to be exclusively Turanian/Turkish, Iranian or Arab, claim a proprietary right to Pakistan; that is why to this school of thought there is an automatic rejection of everything before bin Qasim. So he is particular about excluding these supposed blue-blooded descendants of the steppe (or the desert).
The whole exercise is an attempt to promote the organic unity of the people of the Indus.
This is quite different from the exclusivity of the RSS. They want to exclude a section of the population because that section has a different religion, and because the RSS has determined and satisfied itself that there is scientific reason to exclude those following a different religious authority.