Theoretically, a playlist/mix should be eligible for protection under copyright law. It's just that a copyright only protects a work from being copied. It's different from patents. If two independent people come to the same idea, there is no cause of action between them under copyright law. Someone needs to be able to show by a preponderance of the evidence someone copied someone else. It would be hard to prove someone 'copied' a playlist. It works with easier with recordings or specific songs, but I'm sure multiple people would create a playlist with both "Harder Better Faster" and "Get Lucky"

Evidence of Samsung copying Apple could have been useful to support a showing of intentional infringement, but is unnecessary to support a judgment of infringement of a patent. Patent protection is a strong IP protection. It protects against any infringement of the patent no matter how it is derived. Copyright gives the IP holder protection from copying, so it is relatively week. If copying can't be proved there isn't a case for copyright infringement.