Were these abilities just fillers until GF were ready to release these Pokémon with more thought out HA's? We've never had a chance to test the gen II dogs, Zapdos, or Chandelure with any of their original HA's, so what incentive would there be if no one knew if they were OP or rubbish?
This is more of a personal opinion than a hard and fast answer to your question, but if you think about it for a second, it does make sense. If the HA was never released, then it is as good as saying that the Pokemon never had a Hidden Ability in the first place. Changing the Hidden Ability was completely up to Game Freak, and they decided to do it.
In gen V there were a lot of dream world abilities that never got released. So when they finally released the hidden abilities later, they just chose different abilities. Some dream world abilities still haven't been released.