Isn’t the whole body growing from the same point at the same pace in a lot of instances when someone is in the womb (except when something like thalidomide is introduced)? It would seem a big challenge would be to have a part of a human body, at any number of stages after birth, maybe especially after full development, regrow from nothing, and excluding, at the very least, the areas of the body in proximity to it.

I’m obviously not an expert.