Kalyan may be technically out of Mumbai, but not logically. This is because the suburban passengers of Mumbai use Kalyan as a station to take outstation trains. And a train which terminates at Mumbai (CST/BCT/DR/DDR/LTT/Diva/Bandra) are meant not just for Mumbai, they are also for Navi Mumbai, Thane and Panvel, since there is no logical separation between these cities and districts. So halts for Duranto at Dadar/Thane/Kalyan/Panvel/Andheri/Borivali are for the benefit of passengers from Mumbai/NaviMumbai/Thane/Panvel together.