To be fair, aluminum isn't typically case-hardened, at least for this application. While I lament the loss of the strength benefits from forging, they may be able to make up for a lot of them by using more material around the wrist pins than on a typical forged piston. 10% weight savings is pretty compelling, as the limiting factor in engine speed is typically con-rod stress.

3D-printed metal parts are already a thing in a number of aerospace applications--I imagine the reliability piece is either fairly well-solved for sintered metal printing, or the parts are expensive enough that we're willing to print each one more than once if required.