Who's "they"? There's no antecedent here. Anyways, not allowing healing would make this deck OP. There has to be a way to keep it in check otherwise, instead of Item lock, people would blame not being able to heal. The only Trainer for Evolutions that needs to be reprinted is Broken Time Space or change the frigging rules that make no sense.
By 'they,' I mean the Pokemon Company people who make these cards in these sets for us to play, of course.