The S10 Plus is the only phone you would be able to get this exclusive skin with, so a regular S10 wouldn't qualify. You can say that Samsung is encouraging people to buy the S10 Plus over the S10, hinting at the newly featured Snapdragon 855 processor can give you a better game play experience. No matter which version of Samsung's new phone you get, it will come with a pair of Samsung ear buds which is also pretty cool (unlike apple).
Samsung devices were the first to be introduced to the mobile fortnite experience, I have yet to try that one out because I am a console strictly gamer. As well as this promotion, Samsung’s also teaming with Epic Games, famous Youtuber and streamer Ninja, and iKon for an upcoming event sometime in March.