See, the Skull Canyon NUC is using a soldered down 8260. This is not a problem for most people using Windows, but for others on alternative operating systems like Linux, new hardware often is not recognized by the latest kernel and needs at least a couple of releases or more before getting supported. In such cases, the option to remove an existing WiFi card and replacing it with an older card compatible with the current kernel is extremely useful.
Skull Canyon continues a not-very-optimistic trend that may very well affect mini-PCs and mITX boards in the future. Is Intel planning to go the soldered route with regards to WiFi hardware? I surely hope not.