This is not at all about "human perception". It's the opposite. The computer is selecting some colors from the picture that it thinks are representative of the color palette used.
When you have a look at the code, the way it is done is that it takes the RGB values as coordinates, randomly selects 3 (or N) clusters, and then caluclates the euclidean distance of all points to their nearest cluster. It continues to randomly select new clusters until it decides that the result doesnt improve anymore at which point it just stops and prints out the coordinates (colors) of the clusters.
It should be immediately clear, that selecting another color model, such as HSL or HSV has a direct impact on the calculated euclidean distance, since these color models are not just simple rotations of the rgb cube. Thus it should lead to other (possibly better) results. I am fairly sure that this is what the parent post was suggesting. The color model used to print out the final colors is/could be independent of the one used internally.