The Reason I Watch HDFCBANK while trading BN

Many of us already know this that HDFCBANK has the highest weightage in BN calculation. But hardly anyone observe HDFCBANK S/R or even simple VWAP, while trading in BN options. If you observe closely then you will realize that their movement is almost similar and since morning HDFC bank is unable to break its VWAP which was more than sufficient sign to short BN.