Air India DEL to SFO nonstop flight was launched in December 2015[1]. So, it's a relatively new route for Air India, and it has been very successful due to its non-stop nature. This change in route (flying over Pacific) was announced back in August 2016[2] itself. They're doing incremental optimization of route plan, nothing wrong in it. There might be permits/permissions required to fly over Chinese air space too, which might have been resolved by now[3].
[1] http://airwaysnews.com/blog/2015/12/07/air-india-inaugurates...
[2] http://www.tribuneindia.com/news/nation/air-india-to-fly-ove...