@Riot Why didn't Surprise Amumu get his own splash art?

I just recently saw the new splash art for the five april fool's skin and had one question. Why did Surprise Party Amumu, a 1350 skin, have to share a splash art? I know that recently the splash team has let 750 skins share a splash (a good idea imo), but shouldn't a higher tier skin get their own time to shine? Even so, I really do like the art, and how you incorporated him into the piece. I just wanted to know the reasoning behind the decision. Thanks!