The official word from support at the epic games store is that:
I would like to inform you that the Epic Games Store team has set up offers in the Store with rules that don’t allow players to purchase a Season Pass, version of a game, or any content that includes something that they already own.
I have checked the Super Deluxe Edition and Season Pass 2, and it appears that both content includes all 4 Multiverse Final Form Cosmetic Packs in both.
That being said, we do not want players to end up spending money on the same content a second time.
I am beyond disgusted.