In the scenario you’re describing (a walled off preserve), said folks could decide to join ‘the space age’ by walking to the next valley if they wanted to.

And that is someone Stone Age folks did regularly, walk to other valleys.

In the real Stone Age, that means they see another group of Stone Age folks. In the space age scenario, that means they get exposure to some space age stuff.

So they’d be making the choice to stay, by staying, if they don’t do that.

No one is building a fence to keep them in, just like no one was working to keep ‘the man of the hole’ in. If someone does make a fenced off area around them that is impossible to escape, then sure that could be a problem. It’s a prison then.

But that’s not what anyone is proposing I can see.

They were just working to keep others from going in and screwing with him.

He knew there were others out there, he just didn’t want to be bothered - and they were trying to help him do that.