Crown has forced me - and I suspect many others - to reappraise how some very fundamental aspects of Dominion work. Which may be part of the confusion.
I'd always thought that Action cards had an "on-play-as-action" trigger that did did something, and Treasures had an "on-play-as-treasure" trigger that did something. In your Action phase, for so long as you still had action quota available, you could play a card from your hand as an Action, if it had the Action type. Then, in your Buy phase, you could play as many cards from your hand as you liked as Treasures, if they had the Treasure type.
By this way of thinking, when you play Black Market or Storyteller, you then get to play some cards as Treasures.
So I - and I suspect many others - assumed that if we ever saw an Action-Treasure card, it would have an on-play-as-action trigger which did one thing and an on-play-as-treasure trigger which did something different. If you played it on Black Market or Storyteller, it would on-play-as-treasure.
But it turns out it's not really like that at all. Instead, cards have a single "on-play" trigger. You never play a card as an Action or as a Treasure, and when you play Crown what matters is whether you're in the Action or the Buy phase. We live and learn.