Just an FYI: In 11.0.0, Blizzard changed the C_PetBattles.GetBreedQuality to be indexed from 0. However, all other functions related to pet quality is still indexed from 1. So until everything is changed, most authors are just adding 1 to the result.

ie:
local rarity = C_PetBattles.GetBreedQuality(petInfo.petOwner, petInfo.petIndex)
should be
local rarity = C_PetBattles.GetBreedQuality(petInfo.petOwner, petInfo.petIndex) + 1

I believe there are 3 locations it needs to be changed.
EnhancedPetBattle.lua - line 667 & 1156
PBTags.lua - line 95