Is the Teemoing shop supposed to be random?

Hey so, I just got onto the league client and looked and saw there was another special offer store thing that Riot has been doing as of late for special events! Sadly, I got skins for 2 champions I have NEVER played before and have no interest playing them either. I thought these were supposed to be based on champions you play a lot but, I got two for champions like I said above that I had no interest playing them. Thanks for help if anyone knows if it's supposed to be random or not. <3 c: