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PPPPS.  Here, for example, are Kulke and Rothermund, in their History of India 4th edition:  The various stages of the indigenous evolution of the Indus civilisation can be documented by an analysis of four sites which have been excavated in more recent years: Mehrgarh, Amari, Kalibangan, Lothal. These four sites reflect the sequence of the four important phases in the protohistory of the northwestern region of the Indian subcontinent. The sequence begins with the transition of nomadic herdsmen to settled agriculturists in eastern Baluchistan, continues with the growth of large villages in the Indus valley and the rise of towns, leads to the emergence of the great cities and, finally, ends with their decline. The first stage is exemplified by Mehrgarh in Baluchistan, the second by Amri in the southern Indus valley and the third and fourth by Kalibangan in Rajasthan and by Lothal in Gujarat.  In other words, the language changes when IVC is discussed.  
PPPPPS Having had a chance to think while I was posting the stuff above, let me say that I'm not wedded to this belief.  You are welcome to add the WP:India tag if you think it will help.  I'm willing to give it another try.  It has been four years after all.  «Talk» "