>>55013545Some level of redundance is ok because it makes sense thematically.
Iron Defense makes sense for "sturdy" Pokémon (Rock or Steel types etc), Acid Armor makes sense for "slimy" or "fluid" Pokémon (Water, certain Poison types, Goodra etc), and as you point out, Barrier makes sense for psychic/mystical Pokémon. Despite being clone moves they aren't really interchangeable - you can't give Acid Armor to Mr. Mime because it just doesn't fit. And removing Barrier takes that option from the latter group.
Same reason why some Pokémon "scratch" while others "pound". You can't just remove "pound" because it's redundant with "scratch" as not every Pokémon has claws.
