Growing human organs in animals in Japan

I can understand harvesting organs from a pig that could be compatible with a person. Because pigs already get slaughtered on a massive scale, so we may as well use their organs if we can.

But I was more concerned with us using rats for the sole purpose of growing an ear for someone like in this video

The mouse isn’t genetically engineered. I might have implied that earlier so I apologize for that. But the mouse does die in this process.

But we have 3D printing technology that can make new body parts like ears now, so I don’t see why we still have to use mice.
It’s a a bit doctor Morroe. I would think the tissue would have to be living , can they do that with printer material ?