The origin of chemical vapor deposition (CVD) growth direction difference in graphene/hexagonal boron nitride (hBN) heterostructures is theoretically studied. The study is focused on the advance in energy gain by H termination of the bare hBN N edge on the Cu(111) surface comparing with that of the bare graphene edge. It is found that the difference in the van der Waals correction method affects largely the advance. However, when the most reliable van der Waals correction of the vdw-DF2-B86R method is used, the results consist with our speculation stating that the edge termination of the existing island rather automatically changes depending on whether the island is graphene or hBN. Thus, it is proposed that the graphene island edge is automatically bare and the hBN island edge is automatically terminated by H during the CVD growth.