There is no better way for a software engineer to learn about the perils of poor software and machine learning than to go under the knife (literally). Cambridge Analytica and the constant fearmongering about data collection ultimately has very few immediate and direct impacts. The designers of Canadian/French radiotherapy machines never had to dogfood their own product. This on the other hand, has a very quick and immediate feedback loop. If one were to graduate from building robots to building e.g. airliner control systems, a bit of skin off the tip of the ear or scalp would pay for itself several times over if you factor in the loss of an airliner.
I get your point, but in this case, that arm is operating on its own without complete control by the user (I assume). Its not the same as playing with something.
It can go very, very wrong if that arm has a bug and there's no force feedback based cutoff.
Modern day razors are very safe and the worst that could happen is a clipped ear or a scratched scalp. Messy yes but hardly deadly. Just remember to restrict the movement state space of the arm so it can never be in front you (don't want it near eyes).
https://www.imgur.com/gallery/r2fW2o7