Thanks for your response!
But is this normal? Because the saturday when I wanted to play, I create 5 differents worlds and the 5 worlds had the same type of spawn, for this reason I think this may be a bug. Unfortunately I delete the worlds and the only one what don't delete was that of the photo.
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Depends on the purpose, if this is done for those maps where the player can't break anything, great, but if this is done for every world in Minecraft (and with "every" I mean a server or common map) I see it pretty useless, the end is protect your things of other players, but they can steal anyway...