That is actually more of an illusion that is exploiting any bit of natural flexibility over a given length.
If you took a circle of rock that is 30cm in diameter, cut it into a spiral at a width of 5mm, you get a length of rock that is now about 14m, but in a coil.
So, if the material had a flex of 1mm per half meter, you would see a total deviation of about 28mm from end to end. The “illusion” part is that while it’s only flexing a small amount, you can see the entire range of flex at once.
It’s still a spring, but it hasn’t actually been significantly bent or reformed. Also, it’s still really cool.