Not trust, but just a belief that the Russian system might be safer from a preemptive hack attack from China.
I believe that during the Kargil conflict, the US switched off the GPS system accessibility on the Indian side of the border, denying the the Indian AF use of GPS munitions. remember, the war was fought wholly on the Indian side of the LOC, both on land and in the air. After this the Indian forces do not trust the Americans.