3d printing rocket engines makes a lot of sense. The engines of Rocket Lab's Electron rocket are 3d printed, Aerojet Rocketdyne's AR1 engines have 3d printed fuel injectors, SpaceX's SuperDraco thrusters (the ones in the Dragon 2 capsules) are 3d printed. Complex geometries with lots of liquid channels make rocket engines difficult to machine, so overcoming the issues with 3d printing heat-resistant parts is well worth it.

But skipping qualification testing is indeed a weird reason. I doubt you can skip test fires.