bilalhaider
Script does not define the language, it is just a skin. It doesn't matter what script was used. Until independence only 9% could actual read or write, if you go back to the 12th century, probably even less.
And afaik Amr Khusrao used to refer to the language he used to write in Hindvi which later got to be known as Hindustani and Hindi/Urdu. Check out
Amir Khusrow - Wikipedia, the free encyclopedia
The word Urdu was not used to describe his poetry even though he wrote in the Nastaliq script.
Similarly Arab traders that came to Kerala wrote Malayalam in the Arabic script as they were more comfortable with it. They also incorporated some Arabic language words. But the language was still Malayalam. It did'nt become Arabic because it was written in Arabic script.