The original idea comes from DeltaRays#0054 on discord:

"...maybe it would be cool to also have caves made with 3d gradient noise, or caves made with cellular automata, aka pseudo-randomly generated 3d grid of values = 0 or 1 and then with a smoothing function they’ll start looking more and more like the caves that are going to be added in 1.17"

This is an additional feature and should not replace the standard caves