Like teeray mentions, if we can define any knot as a path through a Menger Sponge then that path could be realized in a Minecraft world (since it is cube/block/voxel based.)

If you placed minecart rails along the knot plot then you could ride it like a roller coaster.

Maybe this was the initial motivation for the teenagers.

Not parent, but I assume the idea is that you could form this fractal by hand (all or in part) in any 3D Minecraft terrain. Then you could route rails according to the theorem.