@spikeyxxx with your explanation, it becomes clearer: Changing “W” in a “4D” noise offers a relatively easy opportunity to change the noise appearance at the same level of detail, distortion and scale and by this keeping the appearance of the animated noise consistent. You could maybe achieve a similar result with a remapping of the texture coordinates when using “3D” noise but this would be more difficult since you would then have to deal with three values and take care that the transitions are smooth.
