Plus, these seem to be made from interneurons from skin cells. Basically, neurons who transmit signals along the nervous system. I’d be more concerned if they used Pyramidal cells which play more of a role in learning, cognition, and memory.
While interesting, you wouldn’t say that keeping some tissue from the arm alive to be a “horror” on par with a brain in a jar.
Buddy, I hate to tell you this, but that’s literally what your brain does with your arm every single time you move it.