I dont think that core will be added due to Whimsicott not even being ranked on the OUVR lol, this is not actually representive of the meta rn, which is the purpose of the usum ou cores thread, to represent strong cores in the meta.
The team you posted is my absolute favorite team of Pre-USUM meta. Features 4 of the best type (fairy) with 2 of the second best type (steel) with two of my gen 7 faves (kartana and bulu) and my gen 6 waifu (whim). also features awesome cores that define the era (z-bulu + magma tran, terrain + nature power + prankster, pivot koko + scarf kartana) and it's really fun. congrats