Secret Chmapion buffs to promote current skin sales?

Title pretty much says all. I'm not going to go into details because I just want people to share their personal experiences and opinions on this idea. I've noticed for a while now that when new skins and promos come out, the champions in question seem to do overwhelmingly and surprisingly well. Right now I feel like Ashe and Kat are fairing much better against me than they normally do. I remember back when DJ sona came out, a lot of people were playing her and doing VERY WELL. In my opinion, wouldn't people playing these champs actually do generally worse than normal, seeing as most people buying a skin are trying the champion out new or returning to it after having not played it for a while? Wouldn't you expect to do better against champs with new skins because of that idea? Its my personal opinion that when Riot wants to sell one of the new things they introduce to the game, they secretly make slight tweeks and buffs to those specific champions, adding them into the game unannounced. Like making crit% higher, base dps higher, ex. Anything that would make the champ good enough for people to say 'hey that champ is pretty powerful, maybe I want to buy it or buy that new skin for it'. Thoughts?