Please refer to the build-up of the princely state of Jammu & Kashmir, to which every reference to Kashmiri seems to point.
The only authentic Kashmiri in this state was the resident of the Vale. There was clear and unambiguous ethnic and linguistic difference between these 'native' Kashmiris, and the residents of, for instance, the so-called Azad Kashmir, sometimes commonly but inaccurately called Mirpuris. The inhabitants of Baltistan and Gilgit were also ethnically and linguistically distinct. So, too, the denizens of Ladakh and those of Jammu.
As far as I know, the migrations that you and everyone else is referring to are the migrations of the people of 'Azad Kashmir' to the neighbouring regions of Punjab. Please correct me if I am wrong, but few, if any, of the people of the Vale migrated. Few, if any, of the migrants actually spoke Kashur. For some time, I ran a passage of Kashur written in the Latin alphabet as my signature; not one of the patriotic migrated Kashmiris had even a word to say about it.
No, this was the second, the residual proposal; the original was precisely what you articulated: two Muslim homelands within a common nation-state, the rest of that nation-state to be considered, by default, a Hindu homeland.
The agreement between the Muslim League and the INC was based on this kind of architecture; Jinnah promoted it actively because I believe that he saw it as the last chance of escaping partition. Key to the agreement was that the delegates to the Constituent Assembly elected by the Muslim homelands would be bound to follow faithfully the mandate given them by their political foundation, the Muslim League; none of them should be permitted to take a stand in contradiction to, or in opposition to the Muslim League stand.
Quite out of the blue, Nehru declared at a press conference on the 10th of June that delegates to the Constituent Assembly would be free to act as their conscience dictated. That incomprehensible remark, or entirely comprehensive remark, drove Jinnah to ask for partition.
In this narration of events, I have followed Ayesha Jalal.