Unfortunately I think someone misinformed you about the polkadot jersey. That design was created as a sort of "camouflage" for when you inevitably spill or drip a gel or sports drink on yourself mid race. Nothing is as ghastly & uncouth as getting on the podium in a solid jersey with a visible food stain. Thus, the jersey is awarded to the rider who is the sloppiest eater.
There is also one type that you've not mentioned - it is the Continental Champions: Europe and Africa for sure can be seen in Grand Tours.
Unfortunately I think someone misinformed you about the polkadot jersey. That design was created as a sort of "camouflage" for when you inevitably spill or drip a gel or sports drink on yourself mid race. Nothing is as ghastly & uncouth as getting on the podium in a solid jersey with a visible food stain. Thus, the jersey is awarded to the rider who is the sloppiest eater.