From the patch notes:
Global Splash Unification
Updating old splash arts to be the same in all regions. Part one of several.
Splash art is one of most important things we have for conveying a champion's fantasy and personality in League. Splashes are used everywhere: from champ select to the loading screen, portrait icons, the store, and more recently Hextech Crafting. Many of our oldest splash arts are different across the world, meaning those champs and skins have vastly divergent representations of their fantasy and feel, depending on which region you play League in.
While the long-term plan has always been for us to create brand new art for these older pieces, we’re doing some short term work over the next few patches to unify the global experience: some of our splashes will be switching to the Chinese version, and vice versa. We know that in some cases, the quality may still be low or the art style may still be off. Like last year’s Mass Texture Rebalances, this is not a replacement for full-scale splash updates down the road, just a short term solution to solve a specific problem.