Is it as per ACI detailing standard that the pile cap bottom mesh should be 12 inch high and pile steel should enter into pile cap run vertically 12 inch and than bend over pile cap bottom steel.
Our typical pile/pile cap detail calls for 6" of pile embedment and the bottom mat of rebar another 3" above that. This is based on minimum of 3" cover for concrete formed against and exposed to earth. We typically detail the pile reinforcement running up to the underside of the top mat with a 90 degree hook. In my opinion, the hook would not be absolutely necessary as long as you have enough pile cap depth to develop the vertical pile reinforcement. Thus the reason for the hooked bar.