The only thing custom in it is the naming, the GT2 is a single slice iGPU there is nothing to enable in it over the 615 which is already a full slice my bet is

The only thing custom in it is the naming, the GT2 is a single slice iGPU there is nothing to enable in it over the 615 which is already a full slice my bet is that if there is any difference is that the 617 has a boost clock of 1100 instead of 1050mhz or something silly like this.