No, these ones are bigger. Not sure how it works. Guess it must work kinda like a regular spawner, but I'm not really sure how those work either.

[He's not smart enough to understand what goes on when he tells his spawner to make something. All he knows is that it makes food appear, and that's fine with him. He's less fine with the skeletons appearing every night, but there's not much he can do about that.]

They're not off-limits, no. Probably not a good idea to go wandering around them without a guide though.